diff --git a/docs/plan.md b/docs/plan.md
index a9526ed..82733a1 100644
--- a/docs/plan.md
+++ b/docs/plan.md
@@ -12,7 +12,7 @@ Cross-references: `architecture.md` (design), `requirements.md` (REQ-* citations
 | 4 | Buildings + placement + belt↔building transport | ✅ done |
 | 5 | Scrap + ships skeleton (data + spawning, no AI) | ✅ done |
 | 6 | Ship behavior systems + movement arbitration | ✅ done |
-| 7 | Waves, threat accumulation, combat resolution, deaths & loot | ⬜ |
+| 7 | Waves, threat accumulation, combat resolution, deaths & loot | ✅ done |
 | 8 | UI layer (GameWorldView, visuals.toml, panels, build/demolish, speed controls) | ⬜ |
 
 Tick order reference (architecture.md §Tick Order):
diff --git a/src/lib/sim/Building.h b/src/lib/sim/Building.h
index 84af0bb..43833d8 100644
--- a/src/lib/sim/Building.h
+++ b/src/lib/sim/Building.h
@@ -52,6 +52,17 @@ struct ConstructionSite
     Tick         completesAt   = 0;             // 0 = queued but not yet started
 };
 
+// Weapon state for stationary structures (defence stations).
+// Distinct from Ship::Weapon; stations have no movement intent.
+struct StationWeapon
+{
+    float damage;
+    float range;
+    float fireRateHz;
+    float cooldownTicks;
+    std::optional<EntityId> currentTarget;
+};
+
 // A fully constructed, operational building.
 struct Building
 {
@@ -73,4 +84,7 @@ struct Building
     std::vector<Port>   outputPorts;
     std::vector<Port>   inputPorts;  // perimeter tiles (minus output-port tiles),
                                      // direction pointing INTO building
+
+    // Set only for defence stations; nullopt for all other building types.
+    std::optional<StationWeapon> weapon;
 };
diff --git a/src/lib/sim/BuildingSystem.cpp b/src/lib/sim/BuildingSystem.cpp
index c0209ef..da15b97 100644
--- a/src/lib/sim/BuildingSystem.cpp
+++ b/src/lib/sim/BuildingSystem.cpp
@@ -718,3 +718,90 @@ void BuildingSystem::healBuilding(EntityId id, float amount)
         }
     }
 }
+
+void BuildingSystem::damageBuilding(EntityId id, float amount)
+{
+    for (Building& b : m_buildings)
+    {
+        if (b.id == id)
+        {
+            b.hp -= amount;
+            return;
+        }
+    }
+}
+
+EntityId BuildingSystem::placeImmediate(BuildingType type,
+                                         const std::vector<std::string>& surfaceMask,
+                                         QPoint anchor, Rotation rotation,
+                                         float hp, float maxHp)
+{
+    const EntityId id = m_allocateId();
+    const ParsedSurfaceMask mask = parseSurfaceMask(surfaceMask, rotation);
+
+    Building building;
+    building.id        = id;
+    building.anchor    = anchor;
+    building.footprint = mask.footprint;
+    building.rotation  = rotation;
+    building.type      = type;
+    building.hp        = hp;
+    building.maxHp     = maxHp;
+
+    for (const QPoint& cell : mask.bodyCells)
+    {
+        const QPoint absCell = anchor + cell;
+        building.bodyCells.push_back(absCell);
+        m_tileOccupancy[{absCell.x(), absCell.y()}] = id;
+    }
+    for (const Port& port : mask.outputPorts)
+    {
+        Port absPort;
+        absPort.tile      = anchor + port.tile;
+        absPort.direction = port.direction;
+        building.outputPorts.push_back(absPort);
+    }
+    building.inputPorts = computeInputPorts(building);
+
+    m_buildings.push_back(std::move(building));
+    return id;
+}
+
+bool BuildingSystem::removeBuilding(EntityId id)
+{
+    for (std::vector<Building>::iterator it = m_buildings.begin();
+         it != m_buildings.end();
+         ++it)
+    {
+        if (it->id == id)
+        {
+            for (const QPoint& cell : it->bodyCells)
+            {
+                m_tileOccupancy.erase({cell.x(), cell.y()});
+            }
+            m_buildings.erase(it);
+            return true;
+        }
+    }
+    return false;
+}
+
+void BuildingSystem::initStationWeapon(EntityId id, const StationWeapon& weapon)
+{
+    for (Building& b : m_buildings)
+    {
+        if (b.id == id)
+        {
+            b.weapon = weapon;
+            return;
+        }
+    }
+}
+
+void BuildingSystem::forEachBuilding(std::function<void(Building&)> fn)
+{
+    for (Building& b : m_buildings)
+    {
+        fn(b);
+    }
+}
diff --git a/src/lib/sim/BuildingSystem.h b/src/lib/sim/BuildingSystem.h
index 7e08c05..f4c1623 100644
--- a/src/lib/sim/BuildingSystem.h
+++ b/src/lib/sim/BuildingSystem.h
@@ -71,6 +71,27 @@ public:
     // Increase a building's HP by amount, clamped to maxHp.
     void healBuilding(EntityId id, float amount);
 
+    // Reduce a building's HP by amount; hp may go below 0 (step 9 processes deaths).
+    void damageBuilding(EntityId id, float amount);
+
+    // Bypass the construction queue and create a fully-operational Building
+    // immediately. Used for pre-placed structures (HQ, defence stations).
+    // surfaceMask comes from the relevant config struct.
+    EntityId placeImmediate(BuildingType type,
+                            const std::vector<std::string>& surfaceMask,
+                            QPoint anchor, Rotation rotation,
+                            float hp, float maxHp);
+
+    // Remove an operational building by id without refund (used for deaths).
+    // Returns true if found and removed.
+    bool removeBuilding(EntityId id);
+
+    // Set the weapon component on an already-placed defence station.
+    void initStationWeapon(EntityId id, const StationWeapon& weapon);
+
+    // Mutable iteration over all operational buildings (used by CombatSystem).
+    void forEachBuilding(std::function<void(Building&)> fn);
+
 private:
     struct BeltEntry
     {
diff --git a/src/lib/sim/CMakeLists.txt b/src/lib/sim/CMakeLists.txt
index 339ee67..d7f75a5 100644
--- a/src/lib/sim/CMakeLists.txt
+++ b/src/lib/sim/CMakeLists.txt
@@ -9,6 +9,8 @@ SET(HDRS
     ${CMAKE_CURRENT_SOURCE_DIR}/Ship.h
     ${CMAKE_CURRENT_SOURCE_DIR}/ShipSystem.h
     ${CMAKE_CURRENT_SOURCE_DIR}/ScrapSystem.h
+    ${CMAKE_CURRENT_SOURCE_DIR}/WaveSystem.h
+    ${CMAKE_CURRENT_SOURCE_DIR}/CombatSystem.h
     PARENT_SCOPE
 )
 
@@ -20,6 +22,8 @@ SET(SRCS
     ${CMAKE_CURRENT_SOURCE_DIR}/BuildingSystem.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/ShipSystem.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/ScrapSystem.cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/WaveSystem.cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/CombatSystem.cpp
     PARENT_SCOPE
 )
 
diff --git a/src/lib/sim/CombatSystem.cpp b/src/lib/sim/CombatSystem.cpp
new file mode 100644
index 0000000..b1cb40d
--- /dev/null
+++ b/src/lib/sim/CombatSystem.cpp
@@ -0,0 +1,246 @@
+#include "CombatSystem.h"
+
+#include "BuildingSystem.h"
+#include "BuildingType.h"
+#include "Ship.h"
+#include "ShipSystem.h"
+
+CombatSystem::CombatSystem(const GameConfig& config)
+    : m_config(config)
+{
+}
+
+void CombatSystem::tick(Tick currentTick,
+                         ShipSystem& ships,
+                         BuildingSystem& buildings,
+                         std::vector<FireEvent>& outFireEvents)
+{
+    // Ships: iterate and resolve weapon for each combat ship.
+    ships.forEach([&](Ship& ship)
+    {
+        resolveShipWeapon(ship, currentTick, ships, buildings, outFireEvents);
+    });
+
+    // Defence stations: acquire targets and fire.
+    buildings.forEachBuilding([&](Building& building)
+    {
+        if (building.type == BuildingType::PlayerDefenceStation ||
+            building.type == BuildingType::EnemyDefenceStation)
+        {
+            resolveStationWeapon(building, currentTick, ships, buildings, outFireEvents);
+        }
+    });
+}
+
+void CombatSystem::resolveShipWeapon(Ship& ship, Tick currentTick,
+                                      ShipSystem& ships,
+                                      BuildingSystem& buildings,
+                                      std::vector<FireEvent>& out)
+{
+    if (!ship.weapon || !ship.threatResponse ||
+        !ship.threatResponse->currentTarget)
+    {
+        return;
+    }
+
+    Weapon& w = *ship.weapon;
+
+    // Decrement cooldown toward zero.
+    if (w.cooldownTicks > 0.0f)
+    {
+        w.cooldownTicks -= 1.0f;
+    }
+
+    if (w.cooldownTicks > 0.0f)
+    {
+        return;
+    }
+
+    const EntityId targetId = *ship.threatResponse->currentTarget;
+
+    const std::optional<QVector2D> tPos = targetPosition(targetId, ships, buildings);
+    if (!tPos)
+    {
+        ship.threatResponse->currentTarget = std::nullopt;
+        return;
+    }
+
+    const float dist = (ship.position - *tPos).length();
+    if (dist > w.range)
+    {
+        return;
+    }
+
+    // Apply damage to the correct pool.
+    if (ships.findShip(targetId))
+    {
+        ships.damageShip(targetId, w.damage);
+    }
+    else
+    {
+        buildings.damageBuilding(targetId, w.damage);
+    }
+
+    FireEvent evt;
+    evt.shooter   = ship.id;
+    evt.target    = targetId;
+    evt.emittedAt = currentTick;
+    out.push_back(evt);
+
+    w.cooldownTicks = static_cast<float>(kTickRateHz) / w.fireRateHz;
+}
+
+void CombatSystem::resolveStationWeapon(Building& station, Tick currentTick,
+                                         ShipSystem& ships,
+                                         BuildingSystem& buildings,
+                                         std::vector<FireEvent>& out)
+{
+    if (!station.weapon)
+    {
+        return;
+    }
+
+    StationWeapon& w = *station.weapon;
+    const bool stationIsEnemy = (station.type == BuildingType::EnemyDefenceStation);
+
+    const QVector2D stationCenter(
+        station.anchor.x() + station.footprint.width()  / 2.0f,
+        station.anchor.y() + station.footprint.height() / 2.0f);
+
+    // Validate or clear existing target.
+    if (w.currentTarget)
+    {
+        const std::optional<QVector2D> tPos =
+            targetPosition(*w.currentTarget, ships, buildings);
+        if (!tPos || (stationCenter - *tPos).length() > w.range)
+        {
+            w.currentTarget = std::nullopt;
+        }
+    }
+
+    // Acquire a new target if needed.
+    if (!w.currentTarget)
+    {
+        w.currentTarget = acquireStationTarget(station, stationIsEnemy,
+                                               ships, buildings);
+    }
+
+    if (!w.currentTarget)
+    {
+        return;
+    }
+
+    // Decrement cooldown.
+    if (w.cooldownTicks > 0.0f)
+    {
+        w.cooldownTicks -= 1.0f;
+    }
+
+    if (w.cooldownTicks > 0.0f)
+    {
+        return;
+    }
+
+    const EntityId targetId = *w.currentTarget;
+    const std::optional<QVector2D> tPos = targetPosition(targetId, ships, buildings);
+    if (!tPos)
+    {
+        w.currentTarget = std::nullopt;
+        return;
+    }
+
+    if ((stationCenter - *tPos).length() > w.range)
+    {
+        return;
+    }
+
+    if (ships.findShip(targetId))
+    {
+        ships.damageShip(targetId, w.damage);
+    }
+    else
+    {
+        buildings.damageBuilding(targetId, w.damage);
+    }
+
+    FireEvent evt;
+    evt.shooter   = station.id;
+    evt.target    = targetId;
+    evt.emittedAt = currentTick;
+    out.push_back(evt);
+
+    w.cooldownTicks = static_cast<float>(kTickRateHz) / w.fireRateHz;
+}
+
+std::optional<EntityId> CombatSystem::acquireStationTarget(
+    const Building& station, bool stationIsEnemy,
+    const ShipSystem& ships,
+    const BuildingSystem& buildings) const
+{
+    const QVector2D stationCenter(
+        station.anchor.x() + station.footprint.width()  / 2.0f,
+        station.anchor.y() + station.footprint.height() / 2.0f);
+    const float range = station.weapon->range;
+
+    std::optional<EntityId> best;
+    float bestDist = range;
+
+    // Scan ships for valid targets.
+    for (const Ship& candidate : ships.allShips())
+    {
+        const bool isValidTarget = stationIsEnemy ? !candidate.isEnemy
+                                                   :  candidate.isEnemy;
+        if (!isValidTarget)
+        {
+            continue;
+        }
+        const float dist = (candidate.position - stationCenter).length();
+        if (dist < bestDist)
+        {
+            bestDist = dist;
+            best     = candidate.id;
+        }
+    }
+
+    // Enemy stations also target player buildings (HQ, PlayerDefenceStation).
+    if (stationIsEnemy)
+    {
+        for (const Building& b : buildings.allBuildings())
+        {
+            if (b.type != BuildingType::Hq &&
+                b.type != BuildingType::PlayerDefenceStation)
+            {
+                continue;
+            }
+            const QVector2D bCenter(b.anchor.x() + b.footprint.width()  / 2.0f,
+                                    b.anchor.y() + b.footprint.height() / 2.0f);
+            const float dist = (bCenter - stationCenter).length();
+            if (dist < bestDist)
+            {
+                bestDist = dist;
+                best     = b.id;
+            }
+        }
+    }
+
+    return best;
+}
+
+std::optional<QVector2D> CombatSystem::targetPosition(
+    EntityId id,
+    const ShipSystem& ships,
+    const BuildingSystem& buildings) const
+{
+    const Ship* ship = ships.findShip(id);
+    if (ship)
+    {
+        return ship->position;
+    }
+    const Building* bld = buildings.findBuilding(id);
+    if (bld)
+    {
+        return QVector2D(bld->anchor.x() + bld->footprint.width()  / 2.0f,
+                         bld->anchor.y() + bld->footprint.height() / 2.0f);
+    }
+    return std::nullopt;
+}
diff --git a/src/lib/sim/CombatSystem.h b/src/lib/sim/CombatSystem.h
new file mode 100644
index 0000000..5ba3e34
--- /dev/null
+++ b/src/lib/sim/CombatSystem.h
@@ -0,0 +1,61 @@
+#pragma once
+
+#include <optional>
+#include <vector>
+
+#include <QVector2D>
+
+#include "Building.h"
+#include "EntityId.h"
+#include "FireEvent.h"
+#include "GameConfig.h"
+#include "Ship.h"
+#include "Tick.h"
+
+class BuildingSystem;
+class ShipSystem;
+
+// Resolves all weapon fire for ships and defence stations (tick-order step 8).
+// REQ-SHP-FIRING, REQ-DEF-PLAYER-FIRE, REQ-DEF-ENEMY-FIRE.
+class CombatSystem
+{
+public:
+    explicit CombatSystem(const GameConfig& config);
+
+    // Advance weapon cooldowns, acquire targets for stations, fire when ready,
+    // apply damage, and append FireEvents. Damage is applied immediately via
+    // ShipSystem::damageShip and BuildingSystem::damageBuilding; step 9
+    // removes entities whose HP dropped to zero or below.
+    void tick(Tick currentTick,
+              ShipSystem& ships,
+              BuildingSystem& buildings,
+              std::vector<FireEvent>& outFireEvents);
+
+private:
+    // Process one ship's weapon for this tick.
+    void resolveShipWeapon(Ship& ship, Tick currentTick,
+                           ShipSystem& ships,
+                           BuildingSystem& buildings,
+                           std::vector<FireEvent>& out);
+
+    // Process one defence-station's weapon for this tick.
+    void resolveStationWeapon(Building& station, Tick currentTick,
+                              ShipSystem& ships,
+                              BuildingSystem& buildings,
+                              std::vector<FireEvent>& out);
+
+    // Find the nearest valid target for a defence station within its range.
+    // Enemy stations target player ships + HQ + PlayerDefenceStation.
+    // Player stations target enemy ships only.
+    std::optional<EntityId> acquireStationTarget(
+        const Building& station, bool stationIsEnemy,
+        const ShipSystem& ships,
+        const BuildingSystem& buildings) const;
+
+    // Return the world position of the entity, or nullopt if it no longer exists.
+    std::optional<QVector2D> targetPosition(EntityId id,
+                                            const ShipSystem& ships,
+                                            const BuildingSystem& buildings) const;
+
+    const GameConfig& m_config;
+};
diff --git a/src/lib/sim/ShipSystem.cpp b/src/lib/sim/ShipSystem.cpp
index fd11cab..b6c7f8a 100644
--- a/src/lib/sim/ShipSystem.cpp
+++ b/src/lib/sim/ShipSystem.cpp
@@ -173,6 +173,19 @@ bool ShipSystem::healShip(EntityId id, float amount)
     return false;
 }
 
+bool ShipSystem::damageShip(EntityId id, float amount)
+{
+    for (Ship& s : m_ships)
+    {
+        if (s.id == id)
+        {
+            s.hp -= amount;
+            return true;
+        }
+    }
+    return false;
+}
+
 // ---------------------------------------------------------------------------
 // clearMovementIntents
 // ---------------------------------------------------------------------------
diff --git a/src/lib/sim/ShipSystem.h b/src/lib/sim/ShipSystem.h
index fb56cb9..0a96f0b 100644
--- a/src/lib/sim/ShipSystem.h
+++ b/src/lib/sim/ShipSystem.h
@@ -47,6 +47,10 @@ public:
     // -- Movement (tick-order step 10) ---------------------------------------
     void tickMovement();
 
+    // Reduce ship HP by amount. Does not remove the ship; step 9 handles death.
+    // Returns false if ship not found.
+    bool damageShip(EntityId id, float amount);
+
 private:
     const ShipDef* findShipDef(const std::string& blueprintId) const;
 
diff --git a/src/lib/sim/Simulation.cpp b/src/lib/sim/Simulation.cpp
index 53c8f62..a17065c 100644
--- a/src/lib/sim/Simulation.cpp
+++ b/src/lib/sim/Simulation.cpp
@@ -1,8 +1,13 @@
 #include "Simulation.h"
 
+#include <cassert>
+
 #include "BuildingSystem.h"
+#include "CombatSystem.h"
 #include "ScrapSystem.h"
 #include "ShipSystem.h"
+#include "SurfaceMask.h"
+#include "WaveSystem.h"
 
 Simulation::Simulation(const GameConfig& config, unsigned int seed)
     : m_config(config)
@@ -10,8 +15,15 @@ Simulation::Simulation(const GameConfig& config, unsigned int seed)
     , m_currentTick(0)
     , m_nextId(1)
     , m_buildingBlocksStock(config.world.startingBuildingBlocks)
+    , m_gameOver(false)
+    , m_hqId(kInvalidEntityId)
+    , m_playerStation1Id(kInvalidEntityId)
+    , m_playerStation2Id(kInvalidEntityId)
     , m_beltSystem(config.world.beltSpeedTilesPerSecond)
 {
+    m_currentEnemyStationIds[0] = kInvalidEntityId;
+    m_currentEnemyStationIds[1] = kInvalidEntityId;
+
     m_buildingSystem = std::make_unique<BuildingSystem>(
         config,
         m_beltSystem,
@@ -20,35 +32,303 @@ Simulation::Simulation(const GameConfig& config, unsigned int seed)
         m_rng);
     m_shipSystem  = std::make_unique<ShipSystem>(config, [this]() { return allocateId(); });
     m_scrapSystem = std::make_unique<ScrapSystem>([this]() { return allocateId(); });
+    m_waveSystem  = std::make_unique<WaveSystem>(config, m_rng);
+    m_combatSystem = std::make_unique<CombatSystem>(config);
+
+    // Initialize blueprint unlock state.
+    for (const ShipDef& def : config.ships.ships)
+    {
+        BlueprintState state;
+        state.unlocked = def.availableFromStart;
+        state.level    = def.availableFromStart ? def.blueprint.playerProductionLevel : 0;
+        m_blueprintLevels[def.id] = state;
+    }
+
+    placeInitialStructures();
 }
 
 Simulation::~Simulation() = default;
 
+// ---------------------------------------------------------------------------
+// tick
+// ---------------------------------------------------------------------------
+
 void Simulation::tick()
 {
-    m_buildingSystem->tickConstruction(m_currentTick);
-    m_buildingSystem->tickBeltPull();                        // tick order step 3
-    m_buildingSystem->tickProduction(m_currentTick);         // step 4
-    m_buildingSystem->tickBeltPush();                        // step 5
-    m_beltSystem.tick();                                     // step 6
+    // Step 1: wave scheduler
+    m_waveSystem->tickWaveScheduler(m_currentTick, *m_shipSystem,
+                                    m_config.world.heightTiles);
 
-    // Step 7: ship behavior systems (movement arbitration via intent priority).
+    // Step 2: threat accumulation
+    m_waveSystem->tickThreatAccumulation(m_currentTick);
+
+    // Construction + production pipeline
+    m_buildingSystem->tickConstruction(m_currentTick);
+    m_buildingSystem->tickBeltPull();                    // step 3
+    m_buildingSystem->tickProduction(m_currentTick);     // step 4
+    m_buildingSystem->tickBeltPush();                    // step 5
+    m_beltSystem.tick();                                 // step 6
+
+    // Step 7: ship behavior systems (movement arbitration via intent priority)
     m_shipSystem->clearMovementIntents();
     m_shipSystem->tickHomeReturn();                          // priority 4
     m_shipSystem->tickThreatResponse(*m_buildingSystem);     // priority 3
     m_shipSystem->tickRepairBehavior(*m_buildingSystem);     // priority 2
     m_shipSystem->tickScrapCollector(*m_scrapSystem, *m_buildingSystem);  // priority 1
 
-    // Steps 8 & 9: combat resolution and deaths — added in implementation step 7.
+    // Step 8: combat resolution
+    m_combatSystem->tick(m_currentTick, *m_shipSystem,
+                         *m_buildingSystem, m_fireEvents);
 
-    // Step 10: advance ship positions from winning intents.
+    // Step 9: deaths & loot
+    if (!m_gameOver)
+    {
+        tickDeathsAndLoot();
+    }
+
+    // Step 10: advance ship positions
     m_shipSystem->tickMovement();
 
-    m_scrapSystem->tickDespawn(m_currentTick);               // step 11
+    // Step 11: scrap despawn
+    m_scrapSystem->tickDespawn(m_currentTick);
 
     ++m_currentTick;
 }
 
+// ---------------------------------------------------------------------------
+// Pre-placement
+// ---------------------------------------------------------------------------
+
+void Simulation::placeInitialStructures()
+{
+    // HQ — right edge of asteroid (rightmost asteroid tile is x = -1).
+    const ParsedSurfaceMask hqParsed =
+        parseSurfaceMask(m_config.stations.hq.surfaceMask, Rotation::East);
+    const int hqAnchorX = -hqParsed.footprint.width();
+    const int hqAnchorY =
+        (m_config.world.heightTiles - hqParsed.footprint.height()) / 2;
+    const float hqHp =
+        static_cast<float>(m_config.stations.hq.hpFormula.evaluate(0.0));
+    m_hqId = m_buildingSystem->placeImmediate(
+        BuildingType::Hq,
+        m_config.stations.hq.surfaceMask,
+        QPoint(hqAnchorX, hqAnchorY),
+        Rotation::East, hqHp, hqHp);
+
+    // Player defence stations — right edge of player buffer zone.
+    const ParsedSurfaceMask psParsed =
+        parseSurfaceMask(m_config.stations.playerStation.surfaceMask, Rotation::East);
+    const int psAnchorX =
+        m_config.world.regions.playerBufferWidth - psParsed.footprint.width();
+    const double psLevel = static_cast<double>(m_config.stations.playerStation.level);
+    const float psHp = static_cast<float>(
+        m_config.stations.playerStation.hpFormula.evaluate(psLevel));
+
+    StationWeapon psWeapon;
+    psWeapon.damage        = static_cast<float>(
+        m_config.stations.playerStation.damageFormula.evaluate(psLevel));
+    psWeapon.range         = static_cast<float>(
+        m_config.stations.playerStation.rangeFormula.evaluate(psLevel));
+    psWeapon.fireRateHz    = static_cast<float>(
+        m_config.stations.playerStation.fireRateFormula.evaluate(psLevel));
+    psWeapon.cooldownTicks  = 0.0f;
+
+    const int ps1Y = m_config.world.heightTiles / 4;
+    const int ps2Y = 3 * m_config.world.heightTiles / 4;
+
+    m_playerStation1Id = m_buildingSystem->placeImmediate(
+        BuildingType::PlayerDefenceStation,
+        m_config.stations.playerStation.surfaceMask,
+        QPoint(psAnchorX, ps1Y), Rotation::East, psHp, psHp);
+    m_buildingSystem->initStationWeapon(m_playerStation1Id, psWeapon);
+
+    m_playerStation2Id = m_buildingSystem->placeImmediate(
+        BuildingType::PlayerDefenceStation,
+        m_config.stations.playerStation.surfaceMask,
+        QPoint(psAnchorX, ps2Y), Rotation::East, psHp, psHp);
+    m_buildingSystem->initStationWeapon(m_playerStation2Id, psWeapon);
+
+    // Enemy defence stations — generation 0 (initial set).
+    placeEnemyStationSet(0);
+}
+
+void Simulation::placeEnemyStationSet(int generation)
+{
+    const ParsedSurfaceMask esParsed =
+        parseSurfaceMask(m_config.stations.enemyStation.surfaceMask, Rotation::East);
+
+    // Right edge of contest zone, shifted right by (generation * pushExpandColumns).
+    const int rightEdgeX = m_config.world.regions.playerBufferWidth
+                         + m_config.world.regions.contestZoneWidth
+                         + generation * m_config.world.push.pushExpandColumns;
+    const int anchorX = rightEdgeX - esParsed.footprint.width();
+
+    const double genD = static_cast<double>(generation);
+    const float esHp  = static_cast<float>(
+        m_config.stations.enemyStation.hpFormula.evaluate(genD));
+
+    StationWeapon esWeapon;
+    esWeapon.damage        = static_cast<float>(
+        m_config.stations.enemyStation.damageFormula.evaluate(genD));
+    esWeapon.range         = static_cast<float>(
+        m_config.stations.enemyStation.rangeFormula.evaluate(genD));
+    esWeapon.fireRateHz    = static_cast<float>(
+        m_config.stations.enemyStation.fireRateFormula.evaluate(genD));
+    esWeapon.cooldownTicks  = 0.0f;
+
+    const int y1 = m_config.world.heightTiles / 4;
+    const int y2 = 3 * m_config.world.heightTiles / 4;
+
+    const EntityId id1 = m_buildingSystem->placeImmediate(
+        BuildingType::EnemyDefenceStation,
+        m_config.stations.enemyStation.surfaceMask,
+        QPoint(anchorX, y1), Rotation::East, esHp, esHp);
+    m_buildingSystem->initStationWeapon(id1, esWeapon);
+
+    const EntityId id2 = m_buildingSystem->placeImmediate(
+        BuildingType::EnemyDefenceStation,
+        m_config.stations.enemyStation.surfaceMask,
+        QPoint(anchorX, y2), Rotation::East, esHp, esHp);
+    m_buildingSystem->initStationWeapon(id2, esWeapon);
+
+    m_currentEnemyStationIds[0] = id1;
+    m_currentEnemyStationIds[1] = id2;
+}
+
+// ---------------------------------------------------------------------------
+// Deaths & loot (tick step 9)
+// ---------------------------------------------------------------------------
+
+void Simulation::tickDeathsAndLoot()
+{
+    // --- Dead ships ---
+    std::vector<EntityId> deadShipIds;
+    m_shipSystem->forEach([&deadShipIds](Ship& s)
+    {
+        if (s.hp <= 0.0f)
+        {
+            deadShipIds.push_back(s.id);
+        }
+    });
+
+    for (EntityId deadId : deadShipIds)
+    {
+        const Ship* s = m_shipSystem->findShip(deadId);
+        if (!s)
+        {
+            continue;
+        }
+        // Look up scrap drop amount from config.
+        for (const ShipDef& def : m_config.ships.ships)
+        {
+            if (def.id == s->blueprintId && def.loot.scrapDrop > 0)
+            {
+                const Tick despawnAt = m_currentTick
+                    + secondsToTicks(m_config.world.scrapDespawnSeconds);
+                m_scrapSystem->spawn(s->position, def.loot.scrapDrop, despawnAt);
+                break;
+            }
+        }
+        m_shipSystem->despawn(deadId);
+    }
+
+    // --- Dead buildings (HQ, player/enemy defence stations) ---
+    std::vector<EntityId> deadBuildingIds;
+    for (const Building& b : m_buildingSystem->allBuildings())
+    {
+        if (b.hp <= 0.0f &&
+            (b.type == BuildingType::Hq              ||
+             b.type == BuildingType::PlayerDefenceStation ||
+             b.type == BuildingType::EnemyDefenceStation))
+        {
+            deadBuildingIds.push_back(b.id);
+        }
+    }
+
+    for (EntityId deadId : deadBuildingIds)
+    {
+        const Building* b = m_buildingSystem->findBuilding(deadId);
+        if (!b)
+        {
+            continue;
+        }
+
+        if (b->type == BuildingType::Hq)
+        {
+            m_gameOver = true;
+        }
+        else
+        {
+            const QVector2D center(
+                b->anchor.x() + b->footprint.width()  / 2.0f,
+                b->anchor.y() + b->footprint.height() / 2.0f);
+            const Tick despawnAt = m_currentTick
+                + secondsToTicks(m_config.world.scrapDespawnSeconds);
+            int scrap = 0;
+            if (b->type == BuildingType::PlayerDefenceStation)
+            {
+                const double lv = static_cast<double>(
+                    m_config.stations.playerStation.level);
+                scrap = static_cast<int>(
+                    m_config.stations.playerStation.scrapDropFormula.evaluate(lv));
+            }
+            else if (b->type == BuildingType::EnemyDefenceStation)
+            {
+                const double genD = static_cast<double>(m_waveSystem->generation());
+                scrap = static_cast<int>(
+                    m_config.stations.enemyStation.scrapDropFormula.evaluate(genD));
+            }
+            if (scrap > 0)
+            {
+                m_scrapSystem->spawn(center, scrap, despawnAt);
+            }
+        }
+        m_buildingSystem->removeBuilding(deadId);
+    }
+
+    // --- Push check: if both current enemy stations are gone, trigger push ---
+    const bool es0Gone =
+        (m_buildingSystem->findBuilding(m_currentEnemyStationIds[0]) == nullptr);
+    const bool es1Gone =
+        (m_buildingSystem->findBuilding(m_currentEnemyStationIds[1]) == nullptr);
+
+    if (es0Gone && es1Gone &&
+        m_currentEnemyStationIds[0] != kInvalidEntityId)
+    {
+        m_waveSystem->applyPush();
+        placeEnemyStationSet(m_waveSystem->generation());
+        awardBlueprintDrop();
+    }
+}
+
+void Simulation::awardBlueprintDrop()
+{
+    std::vector<std::string> ids;
+    ids.reserve(m_config.ships.ships.size());
+    for (const ShipDef& def : m_config.ships.ships)
+    {
+        ids.push_back(def.id);
+    }
+
+    std::uniform_int_distribution<int> dist(0, static_cast<int>(ids.size()) - 1);
+    const std::string chosen = ids[static_cast<std::size_t>(dist(m_rng))];
+
+    BlueprintState& state = m_blueprintLevels.at(chosen);
+    const bool wasNew = !state.unlocked;
+    state.unlocked = true;
+    state.level   += 1;
+
+    BlueprintDropEvent evt;
+    evt.blueprintId  = chosen;
+    evt.newLevel     = state.level;
+    evt.wasNewUnlock = wasNew;
+    m_blueprintDropEvents.push_back(evt);
+}
+
+// ---------------------------------------------------------------------------
+// Drains
+// ---------------------------------------------------------------------------
+
 std::vector<FireEvent> Simulation::drainFireEvents()
 {
     std::vector<FireEvent> result;
@@ -63,6 +343,10 @@ std::vector<BlueprintDropEvent> Simulation::drainBlueprintDropEvents()
     return result;
 }
 
+// ---------------------------------------------------------------------------
+// Accessors
+// ---------------------------------------------------------------------------
+
 Tick Simulation::currentTick() const
 {
     return m_currentTick;
@@ -73,6 +357,38 @@ int Simulation::buildingBlocksStock() const
     return m_buildingBlocksStock;
 }
 
+bool Simulation::isGameOver() const
+{
+    return m_gameOver;
+}
+
+double Simulation::threatLevel() const
+{
+    return m_waveSystem->threatLevel();
+}
+
+int Simulation::blueprintLevel(const std::string& shipId) const
+{
+    const std::map<std::string, BlueprintState>::const_iterator it =
+        m_blueprintLevels.find(shipId);
+    if (it == m_blueprintLevels.end())
+    {
+        return 0;
+    }
+    return it->second.level;
+}
+
+bool Simulation::isBlueprintUnlocked(const std::string& shipId) const
+{
+    const std::map<std::string, BlueprintState>::const_iterator it =
+        m_blueprintLevels.find(shipId);
+    if (it == m_blueprintLevels.end())
+    {
+        return false;
+    }
+    return it->second.unlocked;
+}
+
 BuildingSystem& Simulation::buildings()
 {
     return *m_buildingSystem;
diff --git a/src/lib/sim/Simulation.h b/src/lib/sim/Simulation.h
index f3e135d..cbc4d7d 100644
--- a/src/lib/sim/Simulation.h
+++ b/src/lib/sim/Simulation.h
@@ -1,7 +1,9 @@
 #pragma once
 
+#include <map>
 #include <memory>
 #include <random>
+#include <string>
 #include <vector>
 
 #include "BeltSystem.h"
@@ -12,8 +14,10 @@
 #include "Tick.h"
 
 class BuildingSystem;
+class CombatSystem;
 class ShipSystem;
 class ScrapSystem;
+class WaveSystem;
 
 class Simulation
 {
@@ -31,8 +35,14 @@ public:
     // Returns all blueprint drop events since the last drain.
     std::vector<BlueprintDropEvent> drainBlueprintDropEvents();
 
-    Tick currentTick() const;
-    int  buildingBlocksStock() const;
+    Tick   currentTick()          const;
+    int    buildingBlocksStock()  const;
+    bool   isGameOver()           const;
+    double threatLevel()          const;
+
+    // Blueprint state queries.
+    int  blueprintLevel(const std::string& shipId)    const;
+    bool isBlueprintUnlocked(const std::string& shipId) const;
 
     BuildingSystem&       buildings();
     const BuildingSystem& buildings() const;
@@ -46,17 +56,47 @@ public:
 private:
     EntityId allocateId();  // Strictly increasing; never returns kInvalidEntityId.
 
+    // Populate HQ, player defence stations, and the first enemy station set.
+    void placeInitialStructures();
+
+    // Place two enemy defence stations for the given generation level.
+    // Stores their IDs in m_currentEnemyStationIds.
+    void placeEnemyStationSet(int generation);
+
+    // Tick step 9: remove dead ships and buildings, drop scrap, handle push.
+    void tickDeathsAndLoot();
+
+    // Award a random blueprint drop (REQ-DEF-BLUEPRINT-DROP) and emit the event.
+    void awardBlueprintDrop();
+
     const GameConfig& m_config;
     std::mt19937 m_rng;
 
     Tick     m_currentTick;
     EntityId m_nextId;
     int      m_buildingBlocksStock;
+    bool     m_gameOver = false;
+
+    // Pre-placed structure IDs.
+    EntityId m_hqId;
+    EntityId m_playerStation1Id;
+    EntityId m_playerStation2Id;
+    EntityId m_currentEnemyStationIds[2];
+
+    // Blueprint unlock state (REQ-DEF-BLUEPRINT-DROP).
+    struct BlueprintState
+    {
+        bool unlocked;
+        int  level;
+    };
+    std::map<std::string, BlueprintState> m_blueprintLevels;
 
     BeltSystem                      m_beltSystem;
     std::unique_ptr<BuildingSystem> m_buildingSystem;
     std::unique_ptr<ShipSystem>     m_shipSystem;
     std::unique_ptr<ScrapSystem>    m_scrapSystem;
+    std::unique_ptr<WaveSystem>     m_waveSystem;
+    std::unique_ptr<CombatSystem>   m_combatSystem;
 
     std::vector<FireEvent>          m_fireEvents;
     std::vector<BlueprintDropEvent> m_blueprintDropEvents;
diff --git a/src/lib/sim/WaveSystem.cpp b/src/lib/sim/WaveSystem.cpp
new file mode 100644
index 0000000..93413d9
--- /dev/null
+++ b/src/lib/sim/WaveSystem.cpp
@@ -0,0 +1,191 @@
+#include "WaveSystem.h"
+
+#include <algorithm>
+
+#include "ShipSystem.h"
+
+WaveSystem::WaveSystem(const GameConfig& config, std::mt19937& rng)
+    : m_config(config)
+    , m_rng(rng)
+{
+    // Draw the initial inter-wave gap (REQ-WAV-GAP, REQ-WAV-GRACE-PERIOD).
+    m_nextEventTick = drawGapTicks();
+}
+
+void WaveSystem::tickWaveScheduler(Tick currentTick, ShipSystem& ships,
+                                    int worldHeightTiles)
+{
+    if (!m_waveActive)
+    {
+        if (currentTick < m_nextEventTick)
+        {
+            return;
+        }
+        // Gap expired: compose the next wave.
+        m_pendingSpawns = composeWave(currentTick, worldHeightTiles);
+        m_waveActive    = true;
+    }
+
+    // Spawn any ships whose scheduled tick has arrived.
+    std::vector<SpawnEntry> remaining;
+    remaining.reserve(m_pendingSpawns.size());
+    for (const SpawnEntry& entry : m_pendingSpawns)
+    {
+        if (currentTick >= entry.spawnAt)
+        {
+            ships.spawn(entry.blueprintId, entry.level, entry.position,
+                        /*isEnemy=*/true);
+        }
+        else
+        {
+            remaining.push_back(entry);
+        }
+    }
+    m_pendingSpawns = std::move(remaining);
+
+    if (m_pendingSpawns.empty())
+    {
+        m_waveActive    = false;
+        m_nextEventTick = currentTick + drawGapTicks();
+    }
+}
+
+void WaveSystem::tickThreatAccumulation(Tick currentTick)
+{
+    const double elapsedSeconds = static_cast<double>(currentTick) * kTickDurationSeconds;
+    const double rate = m_config.world.waves.threatRateFormula.evaluate(elapsedSeconds);
+    if (rate > 0.0)
+    {
+        m_threatLevel += rate * m_pushScalingMultiplier * kTickDurationSeconds;
+    }
+}
+
+void WaveSystem::applyPush()
+{
+    m_pushScalingMultiplier *= m_config.world.push.scalingFactor;
+    ++m_generation;
+}
+
+double WaveSystem::threatLevel() const
+{
+    return m_threatLevel;
+}
+
+int WaveSystem::generation() const
+{
+    return m_generation;
+}
+
+// ---------------------------------------------------------------------------
+// Private helpers
+// ---------------------------------------------------------------------------
+
+std::vector<WaveSystem::SpawnEntry> WaveSystem::composeWave(Tick currentTick,
+                                                             int worldHeightTiles)
+{
+    const double elapsedSeconds = static_cast<double>(currentTick) * kTickDurationSeconds;
+    const int shipLevel = std::max(1, static_cast<int>(
+        m_config.world.waves.shipLevelFormula.evaluate(elapsedSeconds)));
+
+    // Build eligible ship list with their costs at the current level.
+    struct EligibleShip
+    {
+        std::string blueprintId;
+        double      cost;
+    };
+    std::vector<EligibleShip> eligible;
+    for (const ShipDef& def : m_config.ships.ships)
+    {
+        const double cost = def.threat.costFormula.evaluate(static_cast<double>(shipLevel));
+        if (cost > 0.0)
+        {
+            EligibleShip es;
+            es.blueprintId = def.id;
+            es.cost        = cost;
+            eligible.push_back(es);
+        }
+    }
+
+    if (eligible.empty())
+    {
+        return {};
+    }
+
+    // Take the current threat level as the wave budget and reset it.
+    // Unspent budget is re-added after composition (carry-over).
+    double budget = m_threatLevel;
+    m_threatLevel = 0.0;
+
+    // Enemy spawn buffer X range for the current generation.
+    const float leftX = static_cast<float>(
+        m_config.world.regions.playerBufferWidth
+        + m_config.world.regions.contestZoneWidth
+        + m_generation * m_config.world.push.pushExpandColumns);
+    const float rightX = leftX + static_cast<float>(m_config.world.regions.enemyBufferWidth) - 1.0f;
+
+    std::uniform_real_distribution<float> xDist(leftX, rightX);
+    std::uniform_int_distribution<int>    yDist(0, worldHeightTiles - 1);
+
+    std::vector<SpawnEntry> picked;
+
+    while (true)
+    {
+        // Collect indices of ships whose cost fits the remaining budget.
+        std::vector<std::size_t> fitting;
+        for (std::size_t i = 0; i < eligible.size(); ++i)
+        {
+            if (eligible[i].cost <= budget)
+            {
+                fitting.push_back(i);
+            }
+        }
+        if (fitting.empty())
+        {
+            break;
+        }
+
+        std::uniform_int_distribution<int> pick(0, static_cast<int>(fitting.size()) - 1);
+        const std::size_t chosenIdx = fitting[static_cast<std::size_t>(pick(m_rng))];
+        const EligibleShip& chosen  = eligible[chosenIdx];
+
+        budget -= chosen.cost;
+
+        SpawnEntry entry;
+        entry.blueprintId = chosen.blueprintId;
+        entry.level       = shipLevel;
+        entry.spawnAt     = 0;  // set below after all picks are done
+        entry.position    = QVector2D(xDist(m_rng),
+                                      static_cast<float>(yDist(m_rng)) + 0.5f);
+        picked.push_back(entry);
+    }
+
+    // Carry leftover budget forward to the next wave.
+    m_threatLevel += budget;
+
+    // Spread spawn times evenly across spawnDurationSeconds.
+    const int count = static_cast<int>(picked.size());
+    if (count == 1)
+    {
+        picked[0].spawnAt = currentTick;
+    }
+    else if (count > 1)
+    {
+        const Tick spawnDurationTicks =
+            secondsToTicks(m_config.world.waves.spawnDurationSeconds);
+        for (int i = 0; i < count; ++i)
+        {
+            picked[static_cast<std::size_t>(i)].spawnAt =
+                currentTick + static_cast<Tick>(i) * spawnDurationTicks / (count - 1);
+        }
+    }
+
+    return picked;
+}
+
+Tick WaveSystem::drawGapTicks()
+{
+    const Tick minTicks = secondsToTicks(m_config.world.waves.gapMinSeconds);
+    const Tick maxTicks = secondsToTicks(m_config.world.waves.gapMaxSeconds);
+    std::uniform_int_distribution<Tick> dist(minTicks, maxTicks);
+    return dist(m_rng);
+}
diff --git a/src/lib/sim/WaveSystem.h b/src/lib/sim/WaveSystem.h
new file mode 100644
index 0000000..3304bfd
--- /dev/null
+++ b/src/lib/sim/WaveSystem.h
@@ -0,0 +1,67 @@
+#pragma once
+
+#include <random>
+#include <string>
+#include <vector>
+
+#include <QVector2D>
+
+#include "GameConfig.h"
+#include "Tick.h"
+
+class ShipSystem;
+
+// Manages wave scheduling (tick-order step 1) and threat-level accumulation
+// (tick-order step 2). REQ-WAV-*.
+class WaveSystem
+{
+public:
+    WaveSystem(const GameConfig& config, std::mt19937& rng);
+
+    // Tick step 1: start a new wave when the current gap has expired; spawn
+    // any ships in the pending list whose scheduled tick has arrived.
+    void tickWaveScheduler(Tick currentTick, ShipSystem& ships,
+                           int worldHeightTiles);
+
+    // Tick step 2: accumulate threat from the rate formula, scaled by the
+    // current push multiplier (REQ-WAV-THREAT-RATE, REQ-PSH-ACCUMULATION).
+    void tickThreatAccumulation(Tick currentTick);
+
+    // Called by Simulation (tick step 9) when the current enemy-station set
+    // is fully destroyed: multiplies the push scaling and increments generation.
+    void applyPush();
+
+    double threatLevel() const;
+
+    // Current enemy-station generation level (0 for initial set,
+    // incremented by 1 after each push — REQ-PSH-STATION-STATS).
+    int generation() const;
+
+private:
+    struct SpawnEntry
+    {
+        std::string blueprintId;
+        int         level;
+        Tick        spawnAt;
+        QVector2D   position;
+    };
+
+    // Compose the next wave from the current threat budget, returning timed
+    // spawn entries spread across spawnDurationSeconds.  Leaves any unspent
+    // budget in m_threatLevel (carry-over, REQ-WAV-TRIGGER).
+    std::vector<SpawnEntry> composeWave(Tick currentTick, int worldHeightTiles);
+
+    // Draw a random gap duration in ticks from [gapMin, gapMax].
+    Tick drawGapTicks();
+
+    const GameConfig& m_config;
+    std::mt19937&     m_rng;
+
+    double m_threatLevel           = 0.0;
+    double m_pushScalingMultiplier = 1.0;
+    int    m_generation            = 0;
+
+    bool   m_waveActive    = false;
+    Tick   m_nextEventTick = 0;  // absolute tick when the current gap expires
+    std::vector<SpawnEntry> m_pendingSpawns;
+};
diff --git a/src/test/CMakeLists.txt b/src/test/CMakeLists.txt
index 2828916..88b5f3f 100644
--- a/src/test/CMakeLists.txt
+++ b/src/test/CMakeLists.txt
@@ -12,4 +12,6 @@ add_files(
     ShipTest.cpp
     ScrapTest.cpp
     BehaviorSystemTest.cpp
+    WaveSystemTest.cpp
+    CombatSystemTest.cpp
 )
diff --git a/src/test/CombatSystemTest.cpp b/src/test/CombatSystemTest.cpp
new file mode 100644
index 0000000..6775bc0
--- /dev/null
+++ b/src/test/CombatSystemTest.cpp
@@ -0,0 +1,351 @@
+#include "catch.hpp"
+
+#include <random>
+
+#include "BeltSystem.h"
+#include "Building.h"
+#include "BuildingSystem.h"
+#include "BuildingType.h"
+#include "CombatSystem.h"
+#include "ConfigLoader.h"
+#include "FireEvent.h"
+#include "ScrapSystem.h"
+#include "Ship.h"
+#include "ShipSystem.h"
+#include "Simulation.h"
+#include "Tick.h"
+
+static GameConfig loadConfig()
+{
+    return ConfigLoader::loadFromDirectory(DOTA_FACTORY_CONFIG_DIR);
+}
+
+// Find the first ShipDef with a combat component.
+static const ShipDef* findCombatShip(const GameConfig& cfg)
+{
+    for (const ShipDef& def : cfg.ships.ships)
+    {
+        if (def.combat)
+        {
+            return &def;
+        }
+    }
+    return nullptr;
+}
+
+// ---------------------------------------------------------------------------
+// Ship weapon firing
+// ---------------------------------------------------------------------------
+
+TEST_CASE("CombatSystem: ship fires when cooldown=0 and target in range", "[combat]")
+{
+    const GameConfig cfg = loadConfig();
+    std::mt19937 rng(42);
+
+    const ShipDef* combatDef = findCombatShip(cfg);
+    REQUIRE(combatDef != nullptr);
+
+    BeltSystem belts(cfg.world.beltSpeedTilesPerSecond);
+    EntityId nextShipId = 1;
+    EntityId nextBldId  = 100;
+    ShipSystem ships(cfg, [&nextShipId]() { return nextShipId++; });
+    BuildingSystem buildings(cfg, belts,
+        [&nextBldId]() { return nextBldId++; },
+        [](int){},
+        rng);
+
+    // Spawn an enemy combat ship close to the player side.
+    const EntityId enemyId = ships.spawn(combatDef->id, 1,
+        QVector2D(5.0f, 5.0f), /*isEnemy=*/true);
+
+    // Spawn a player combat ship in front of the enemy.
+    const EntityId playerId = ships.spawn(combatDef->id, 1,
+        QVector2D(4.0f, 5.0f), /*isEnemy=*/false);
+
+    // Wire the enemy's weapon target manually.
+    ships.forEach([&](Ship& s)
+    {
+        if (s.id == enemyId && s.weapon)
+        {
+            s.weapon->currentTarget  = playerId;
+            s.weapon->cooldownTicks  = 0.0f;
+            if (s.threatResponse)
+            {
+                s.threatResponse->currentTarget = playerId;
+            }
+        }
+    });
+
+    // Record player HP before combat.
+    float hpBefore = 0.0f;
+    for (const Ship& s : ships.allShips())
+    {
+        if (s.id == playerId) { hpBefore = s.hp; }
+    }
+
+    CombatSystem combat(cfg);
+    std::vector<FireEvent> events;
+    combat.tick(0, ships, buildings, events);
+
+    float hpAfter = 0.0f;
+    for (const Ship& s : ships.allShips())
+    {
+        if (s.id == playerId) { hpAfter = s.hp; }
+    }
+
+    REQUIRE(hpAfter < hpBefore);
+    REQUIRE(events.size() >= 1);
+}
+
+TEST_CASE("CombatSystem: cooldown prevents firing before it expires", "[combat]")
+{
+    const GameConfig cfg = loadConfig();
+    std::mt19937 rng(42);
+
+    const ShipDef* combatDef = findCombatShip(cfg);
+    REQUIRE(combatDef != nullptr);
+
+    BeltSystem belts(cfg.world.beltSpeedTilesPerSecond);
+    EntityId nextShipId = 1;
+    EntityId nextBldId  = 100;
+    ShipSystem ships(cfg, [&nextShipId]() { return nextShipId++; });
+    BuildingSystem buildings(cfg, belts,
+        [&nextBldId]() { return nextBldId++; },
+        [](int){},
+        rng);
+
+    const EntityId enemyId  = ships.spawn(combatDef->id, 1, QVector2D(5.0f, 5.0f), true);
+    const EntityId playerId = ships.spawn(combatDef->id, 1, QVector2D(4.0f, 5.0f), false);
+
+    // Set cooldown to 3 so it won't fire on tick 0 or 1 or 2.
+    ships.forEach([&](Ship& s)
+    {
+        if (s.id == enemyId && s.weapon)
+        {
+            s.weapon->currentTarget = playerId;
+            s.weapon->cooldownTicks = 3.0f;
+            if (s.threatResponse)
+            {
+                s.threatResponse->currentTarget = playerId;
+            }
+        }
+    });
+
+    CombatSystem combat(cfg);
+    std::vector<FireEvent> events;
+
+    // Ticks 0 and 1: cooldown still > 0 after decrement → no fire.
+    combat.tick(0, ships, buildings, events);
+    combat.tick(1, ships, buildings, events);
+
+    REQUIRE(events.empty());
+
+    // Tick 2: cooldown reaches 0 → fires.
+    combat.tick(2, ships, buildings, events);
+    REQUIRE(events.size() == 1);
+}
+
+TEST_CASE("CombatSystem: no fire when target is out of range", "[combat]")
+{
+    const GameConfig cfg = loadConfig();
+    std::mt19937 rng(42);
+
+    const ShipDef* combatDef = findCombatShip(cfg);
+    REQUIRE(combatDef != nullptr);
+
+    BeltSystem belts(cfg.world.beltSpeedTilesPerSecond);
+    EntityId nextShipId = 1;
+    EntityId nextBldId  = 100;
+    ShipSystem ships(cfg, [&nextShipId]() { return nextShipId++; });
+    BuildingSystem buildings(cfg, belts,
+        [&nextBldId]() { return nextBldId++; },
+        [](int){},
+        rng);
+
+    const EntityId enemyId  = ships.spawn(combatDef->id, 1, QVector2D(0.0f,   0.0f), true);
+    const EntityId playerId = ships.spawn(combatDef->id, 1, QVector2D(500.0f, 0.0f), false);
+
+    ships.forEach([&](Ship& s)
+    {
+        if (s.id == enemyId && s.weapon)
+        {
+            s.weapon->currentTarget = playerId;
+            s.weapon->cooldownTicks = 0.0f;
+            if (s.threatResponse)
+            {
+                s.threatResponse->currentTarget = playerId;
+            }
+        }
+    });
+
+    CombatSystem combat(cfg);
+    std::vector<FireEvent> events;
+    combat.tick(0, ships, buildings, events);
+
+    REQUIRE(events.empty());
+}
+
+// ---------------------------------------------------------------------------
+// Station weapon firing
+// ---------------------------------------------------------------------------
+
+TEST_CASE("CombatSystem: player station fires at enemy ship in range", "[combat]")
+{
+    const GameConfig cfg = loadConfig();
+    Simulation sim(cfg, 42);
+
+    // Find the player defence station.
+    EntityId stationId = kInvalidEntityId;
+    for (const Building& b : sim.buildings().allBuildings())
+    {
+        if (b.type == BuildingType::PlayerDefenceStation)
+        {
+            stationId = b.id;
+            break;
+        }
+    }
+    REQUIRE(stationId != kInvalidEntityId);
+
+    // Place an enemy ship close to the player station.
+    QVector2D stationCenter;
+    for (const Building& b : sim.buildings().allBuildings())
+    {
+        if (b.id == stationId)
+        {
+            stationCenter = QVector2D(
+                b.anchor.x() + b.footprint.width()  / 2.0f,
+                b.anchor.y() + b.footprint.height() / 2.0f);
+            break;
+        }
+    }
+
+    // Find a combat ship blueprint for the enemy.
+    const ShipDef* combatDef = findCombatShip(cfg);
+    REQUIRE(combatDef != nullptr);
+
+    const EntityId enemyId = sim.ships().spawn(
+        combatDef->id, 1,
+        QVector2D(stationCenter.x() + 1.0f, stationCenter.y()),
+        /*isEnemy=*/true);
+
+    // Tick to let station auto-acquire and fire.
+    sim.tick();
+
+    // Check that a fire event was emitted with stationId as shooter.
+    const std::vector<FireEvent> events = sim.drainFireEvents();
+    bool stationFired = false;
+    for (const FireEvent& e : events)
+    {
+        if (e.shooter == stationId) { stationFired = true; }
+    }
+    REQUIRE(stationFired);
+}
+
+TEST_CASE("CombatSystem: enemy station fires at player ship in range", "[combat]")
+{
+    const GameConfig cfg = loadConfig();
+    Simulation sim(cfg, 42);
+
+    // Find the enemy defence station.
+    EntityId stationId = kInvalidEntityId;
+    QVector2D stationCenter;
+    for (const Building& b : sim.buildings().allBuildings())
+    {
+        if (b.type == BuildingType::EnemyDefenceStation)
+        {
+            stationId = b.id;
+            stationCenter = QVector2D(
+                b.anchor.x() + b.footprint.width()  / 2.0f,
+                b.anchor.y() + b.footprint.height() / 2.0f);
+            break;
+        }
+    }
+    REQUIRE(stationId != kInvalidEntityId);
+
+    const ShipDef* combatDef = findCombatShip(cfg);
+    REQUIRE(combatDef != nullptr);
+
+    // Spawn a player ship right next to the enemy station.
+    sim.ships().spawn(
+        combatDef->id, 1,
+        QVector2D(stationCenter.x() - 1.0f, stationCenter.y()),
+        /*isEnemy=*/false);
+
+    sim.tick();
+
+    const std::vector<FireEvent> events = sim.drainFireEvents();
+    bool stationFired = false;
+    for (const FireEvent& e : events)
+    {
+        if (e.shooter == stationId) { stationFired = true; }
+    }
+    REQUIRE(stationFired);
+}
+
+// ---------------------------------------------------------------------------
+// Deaths & loot (tick step 9)
+// ---------------------------------------------------------------------------
+
+TEST_CASE("CombatSystem: dead ship is removed after tick step 9", "[combat]")
+{
+    const GameConfig cfg = loadConfig();
+    Simulation sim(cfg, 42);
+
+    const ShipDef* combatDef = findCombatShip(cfg);
+    REQUIRE(combatDef != nullptr);
+
+    const EntityId shipId = sim.ships().spawn(combatDef->id, 1,
+        QVector2D(10.0f, 10.0f));
+
+    // Set hp to lethal.
+    sim.ships().damageShip(shipId, 9999.0f);
+
+    sim.tick();
+
+    REQUIRE(sim.ships().findShip(shipId) == nullptr);
+}
+
+TEST_CASE("CombatSystem: scrap is spawned on ship death", "[combat]")
+{
+    const GameConfig cfg = loadConfig();
+    Simulation sim(cfg, 42);
+
+    // Find a ship def that drops scrap.
+    const ShipDef* droppingDef = nullptr;
+    for (const ShipDef& def : cfg.ships.ships)
+    {
+        if (def.loot.scrapDrop > 0)
+        {
+            droppingDef = &def;
+            break;
+        }
+    }
+    REQUIRE(droppingDef != nullptr);
+
+    const EntityId shipId = sim.ships().spawn(droppingDef->id, 1,
+        QVector2D(10.0f, 10.0f));
+    sim.ships().damageShip(shipId, 9999.0f);
+
+    sim.tick();
+
+    // At least one scrap entity should now exist.
+    REQUIRE(!sim.scraps().allScraps().empty());
+}
+
+TEST_CASE("CombatSystem: HQ death sets game over", "[combat]")
+{
+    const GameConfig cfg = loadConfig();
+    Simulation sim(cfg, 42);
+
+    sim.buildings().forEachBuilding([](Building& b)
+    {
+        if (b.type == BuildingType::Hq)
+        {
+            b.hp = -1.0f;
+        }
+    });
+
+    sim.tick();
+
+    REQUIRE(sim.isGameOver());
+}
diff --git a/src/test/SimulationTest.cpp b/src/test/SimulationTest.cpp
index 0b45c7f..dd7fc2c 100644
--- a/src/test/SimulationTest.cpp
+++ b/src/test/SimulationTest.cpp
@@ -1,17 +1,23 @@
 #include "catch.hpp"
 
+#include "ConfigLoader.h"
 #include "GameConfig.h"
 #include "Simulation.h"
 #include "Tick.h"
 #include "TickDriver.h"
 
+static GameConfig loadConfig()
+{
+    return ConfigLoader::loadFromDirectory(DOTA_FACTORY_CONFIG_DIR);
+}
+
 // ---------------------------------------------------------------------------
 // Simulation
 // ---------------------------------------------------------------------------
 
 TEST_CASE("Simulation::currentTick starts at 0", "[simulation]")
 {
-    const GameConfig config;
+    const GameConfig config = loadConfig();
     const Simulation sim(config);
 
     REQUIRE(sim.currentTick() == 0);
@@ -19,7 +25,7 @@ TEST_CASE("Simulation::currentTick starts at 0", "[simulation]")
 
 TEST_CASE("Simulation::tick increments currentTick by 1", "[simulation]")
 {
-    const GameConfig config;
+    const GameConfig config = loadConfig();
     Simulation sim(config);
 
     sim.tick();
@@ -29,7 +35,7 @@ TEST_CASE("Simulation::tick increments currentTick by 1", "[simulation]")
 
 TEST_CASE("Simulation::tick 10 times yields currentTick == 10", "[simulation]")
 {
-    const GameConfig config;
+    const GameConfig config = loadConfig();
     Simulation sim(config);
 
     for (int i = 0; i < 10; ++i)
@@ -42,7 +48,7 @@ TEST_CASE("Simulation::tick 10 times yields currentTick == 10", "[simulation]")
 
 TEST_CASE("Simulation::drainFireEvents returns empty initially", "[simulation]")
 {
-    const GameConfig config;
+    const GameConfig config = loadConfig();
     Simulation sim(config);
 
     REQUIRE(sim.drainFireEvents().empty());
@@ -50,7 +56,7 @@ TEST_CASE("Simulation::drainFireEvents returns empty initially", "[simulation]")
 
 TEST_CASE("Simulation::drainFireEvents clears queue on drain", "[simulation]")
 {
-    const GameConfig config;
+    const GameConfig config = loadConfig();
     Simulation sim(config);
 
     // First drain: empty.
@@ -62,7 +68,7 @@ TEST_CASE("Simulation::drainFireEvents clears queue on drain", "[simulation]")
 
 TEST_CASE("Simulation::drainBlueprintDropEvents returns empty initially", "[simulation]")
 {
-    const GameConfig config;
+    const GameConfig config = loadConfig();
     Simulation sim(config);
 
     REQUIRE(sim.drainBlueprintDropEvents().empty());
diff --git a/src/test/WaveSystemTest.cpp b/src/test/WaveSystemTest.cpp
new file mode 100644
index 0000000..ad4ca76
--- /dev/null
+++ b/src/test/WaveSystemTest.cpp
@@ -0,0 +1,357 @@
+#include "catch.hpp"
+
+#include <random>
+
+#include "Building.h"
+#include "BuildingSystem.h"
+#include "BuildingType.h"
+#include "ConfigLoader.h"
+#include "Rotation.h"
+#include "Ship.h"
+#include "ShipSystem.h"
+#include "Simulation.h"
+#include "Tick.h"
+#include "WaveSystem.h"
+
+static GameConfig loadConfig()
+{
+    return ConfigLoader::loadFromDirectory(DOTA_FACTORY_CONFIG_DIR);
+}
+
+// ---------------------------------------------------------------------------
+// Threat accumulation
+// ---------------------------------------------------------------------------
+
+TEST_CASE("WaveSystem: threat stays 0 for first 30 game-seconds", "[wave]")
+{
+    const GameConfig cfg = loadConfig();
+    std::mt19937 rng(42);
+    WaveSystem ws(cfg, rng);
+
+    // threat_rate_formula = "1*x - 30", which is <= 0 for x <= 30.
+    const int ticks30s = static_cast<int>(secondsToTicks(30.0));
+    for (int i = 0; i < ticks30s; ++i)
+    {
+        ws.tickThreatAccumulation(static_cast<Tick>(i));
+    }
+
+    REQUIRE(ws.threatLevel() == Approx(0.0));
+}
+
+TEST_CASE("WaveSystem: threat accumulates after 30 game-seconds", "[wave]")
+{
+    const GameConfig cfg = loadConfig();
+    std::mt19937 rng(42);
+    WaveSystem ws(cfg, rng);
+
+    // Run 31 seconds worth of ticks.
+    const int ticks31s = static_cast<int>(secondsToTicks(31.0));
+    for (int i = 0; i < ticks31s; ++i)
+    {
+        ws.tickThreatAccumulation(static_cast<Tick>(i));
+    }
+
+    REQUIRE(ws.threatLevel() > 0.0);
+}
+
+TEST_CASE("WaveSystem: applyPush increases threat accumulation rate", "[wave]")
+{
+    const GameConfig cfg = loadConfig();
+    std::mt19937 rng(42);
+    WaveSystem ws(cfg, rng);
+
+    // Accumulate for 1 tick past the 30s mark to get a baseline rate.
+    const Tick baseTick = secondsToTicks(31.0);
+    ws.tickThreatAccumulation(baseTick);
+    const double levelBefore = ws.threatLevel();
+
+    // Apply push: multiplier should increase.
+    ws.applyPush();
+
+    WaveSystem ws2(cfg, rng);
+    ws2.tickThreatAccumulation(baseTick);
+
+    // After the push the same tick adds more threat.
+    ws.tickThreatAccumulation(baseTick + 1);
+    ws2.tickThreatAccumulation(baseTick + 1);
+
+    // ws has the push multiplier applied; ws2 does not.
+    REQUIRE(ws.threatLevel() > ws2.threatLevel());
+}
+
+TEST_CASE("WaveSystem: generation starts at 0 and increments on push", "[wave]")
+{
+    const GameConfig cfg = loadConfig();
+    std::mt19937 rng(42);
+    WaveSystem ws(cfg, rng);
+
+    REQUIRE(ws.generation() == 0);
+    ws.applyPush();
+    REQUIRE(ws.generation() == 1);
+    ws.applyPush();
+    REQUIRE(ws.generation() == 2);
+}
+
+// ---------------------------------------------------------------------------
+// Pre-placed structures
+// ---------------------------------------------------------------------------
+
+TEST_CASE("WaveSystem: Simulation pre-places HQ + 2 player + 2 enemy stations", "[wave]")
+{
+    const GameConfig cfg = loadConfig();
+    const Simulation sim(cfg, 42);
+
+    int hqCount      = 0;
+    int playerCount  = 0;
+    int enemyCount   = 0;
+    for (const Building& b : sim.buildings().allBuildings())
+    {
+        if (b.type == BuildingType::Hq)                    { ++hqCount; }
+        else if (b.type == BuildingType::PlayerDefenceStation) { ++playerCount; }
+        else if (b.type == BuildingType::EnemyDefenceStation)  { ++enemyCount; }
+    }
+
+    REQUIRE(hqCount     == 1);
+    REQUIRE(playerCount == 2);
+    REQUIRE(enemyCount  == 2);
+}
+
+TEST_CASE("WaveSystem: HQ has correct initial HP from config", "[wave]")
+{
+    const GameConfig cfg = loadConfig();
+    const Simulation sim(cfg, 42);
+
+    const float expectedHp =
+        static_cast<float>(cfg.stations.hq.hpFormula.evaluate(0.0));
+    bool found = false;
+    float actualHp = 0.0f;
+    for (const Building& b : sim.buildings().allBuildings())
+    {
+        if (b.type == BuildingType::Hq)
+        {
+            found    = true;
+            actualHp = b.hp;
+            break;
+        }
+    }
+
+    REQUIRE(found);
+    REQUIRE(actualHp == Approx(expectedHp));
+}
+
+TEST_CASE("WaveSystem: HQ anchor is at asteroid right edge", "[wave]")
+{
+    const GameConfig cfg = loadConfig();
+    const Simulation sim(cfg, 42);
+
+    for (const Building& b : sim.buildings().allBuildings())
+    {
+        if (b.type != BuildingType::Hq) { continue; }
+        // Rightmost body cell must be at x = -1 (asteroid right edge).
+        int maxX = std::numeric_limits<int>::min();
+        for (const QPoint& cell : b.bodyCells)
+        {
+            if (cell.x() > maxX) { maxX = cell.x(); }
+        }
+        REQUIRE(maxX == -1);
+    }
+}
+
+TEST_CASE("WaveSystem: player stations have weapon set", "[wave]")
+{
+    const GameConfig cfg = loadConfig();
+    const Simulation sim(cfg, 42);
+
+    int armedPlayerStations = 0;
+    for (const Building& b : sim.buildings().allBuildings())
+    {
+        if (b.type == BuildingType::PlayerDefenceStation && b.weapon)
+        {
+            ++armedPlayerStations;
+            REQUIRE(b.weapon->damage    > 0.0f);
+            REQUIRE(b.weapon->range     > 0.0f);
+            REQUIRE(b.weapon->fireRateHz > 0.0f);
+        }
+    }
+    REQUIRE(armedPlayerStations == 2);
+}
+
+TEST_CASE("WaveSystem: enemy stations have weapon set", "[wave]")
+{
+    const GameConfig cfg = loadConfig();
+    const Simulation sim(cfg, 42);
+
+    int armedEnemyStations = 0;
+    for (const Building& b : sim.buildings().allBuildings())
+    {
+        if (b.type == BuildingType::EnemyDefenceStation && b.weapon)
+        {
+            ++armedEnemyStations;
+            REQUIRE(b.weapon->damage    > 0.0f);
+            REQUIRE(b.weapon->range     > 0.0f);
+            REQUIRE(b.weapon->fireRateHz > 0.0f);
+        }
+    }
+    REQUIRE(armedEnemyStations == 2);
+}
+
+// ---------------------------------------------------------------------------
+// Wave spawning
+// ---------------------------------------------------------------------------
+
+TEST_CASE("WaveSystem: enemy ships spawn after the initial gap elapses", "[wave]")
+{
+    const GameConfig cfg = loadConfig();
+    Simulation sim(cfg, 42);
+
+    // The maximum gap is gapMaxSeconds = 45s → 1350 ticks.
+    // Run 1500 ticks to guarantee at least one wave has triggered.
+    const int limit = static_cast<int>(secondsToTicks(50.0));
+    for (int i = 0; i < limit; ++i)
+    {
+        sim.tick();
+    }
+
+    bool foundEnemyShip = false;
+    for (const Ship& s : sim.ships().allShips())
+    {
+        if (s.isEnemy)
+        {
+            foundEnemyShip = true;
+            break;
+        }
+    }
+    REQUIRE(foundEnemyShip);
+}
+
+TEST_CASE("WaveSystem: only eligible ships (cost > 0) appear in waves", "[wave]")
+{
+    const GameConfig cfg = loadConfig();
+    Simulation sim(cfg, 42);
+
+    // Run long enough for several waves.
+    const int limit = static_cast<int>(secondsToTicks(120.0));
+    for (int i = 0; i < limit; ++i)
+    {
+        sim.tick();
+    }
+
+    for (const Ship& s : sim.ships().allShips())
+    {
+        if (!s.isEnemy) { continue; }
+        // salvage_ship and repair_ship have cost_formula = "0" and must not spawn.
+        REQUIRE(s.blueprintId != "salvage_ship");
+        REQUIRE(s.blueprintId != "repair_ship");
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Push
+// ---------------------------------------------------------------------------
+
+TEST_CASE("WaveSystem: destroying both enemy stations triggers a push", "[wave]")
+{
+    const GameConfig cfg = loadConfig();
+    Simulation sim(cfg, 42);
+
+    // Damage both enemy stations to 0.
+    sim.buildings().forEachBuilding([](Building& b)
+    {
+        if (b.type == BuildingType::EnemyDefenceStation)
+        {
+            b.hp = -1.0f;
+        }
+    });
+
+    sim.tick();
+
+    // After push: should have 2 new enemy stations.
+    int enemyCount = 0;
+    for (const Building& b : sim.buildings().allBuildings())
+    {
+        if (b.type == BuildingType::EnemyDefenceStation) { ++enemyCount; }
+    }
+    REQUIRE(enemyCount == 2);
+}
+
+TEST_CASE("WaveSystem: push emits exactly one BlueprintDropEvent", "[wave]")
+{
+    const GameConfig cfg = loadConfig();
+    Simulation sim(cfg, 42);
+
+    sim.buildings().forEachBuilding([](Building& b)
+    {
+        if (b.type == BuildingType::EnemyDefenceStation)
+        {
+            b.hp = -1.0f;
+        }
+    });
+
+    sim.tick();
+
+    const std::vector<BlueprintDropEvent> events = sim.drainBlueprintDropEvents();
+    REQUIRE(events.size() == 1);
+}
+
+TEST_CASE("WaveSystem: push blueprint drop awards a known ship id", "[wave]")
+{
+    const GameConfig cfg = loadConfig();
+    Simulation sim(cfg, 42);
+
+    sim.buildings().forEachBuilding([](Building& b)
+    {
+        if (b.type == BuildingType::EnemyDefenceStation)
+        {
+            b.hp = -1.0f;
+        }
+    });
+
+    sim.tick();
+    const std::vector<BlueprintDropEvent> events = sim.drainBlueprintDropEvents();
+    REQUIRE(events.size() == 1);
+
+    bool validId = false;
+    for (const ShipDef& def : cfg.ships.ships)
+    {
+        if (def.id == events[0].blueprintId)
+        {
+            validId = true;
+            break;
+        }
+    }
+    REQUIRE(validId);
+    REQUIRE(events[0].newLevel >= 1);
+}
+
+TEST_CASE("WaveSystem: push places new enemy stations further right", "[wave]")
+{
+    const GameConfig cfg = loadConfig();
+    Simulation sim(cfg, 42);
+
+    // Record the X position of the initial enemy stations.
+    int initialX = std::numeric_limits<int>::min();
+    for (const Building& b : sim.buildings().allBuildings())
+    {
+        if (b.type == BuildingType::EnemyDefenceStation)
+        {
+            if (b.anchor.x() > initialX) { initialX = b.anchor.x(); }
+        }
+    }
+
+    sim.buildings().forEachBuilding([](Building& b)
+    {
+        if (b.type == BuildingType::EnemyDefenceStation) { b.hp = -1.0f; }
+    });
+    sim.tick();
+
+    int newX = std::numeric_limits<int>::min();
+    for (const Building& b : sim.buildings().allBuildings())
+    {
+        if (b.type == BuildingType::EnemyDefenceStation)
+        {
+            if (b.anchor.x() > newX) { newX = b.anchor.x(); }
+        }
+    }
+
+    REQUIRE(newX > initialX);
+}