diff --git a/docs/requirements.md b/docs/requirements.md
index f253fe1..6dfd232 100644
--- a/docs/requirements.md
+++ b/docs/requirements.md
@@ -47,7 +47,7 @@ The following config files drive game parameters:
 - REQ-BLD-9: **Assembler** (3×3): The player selects a recipe from the config-defined crafting tree. Produces the selected output item at the rate defined in recipes.config.
 - REQ-BLD-10: **Reprocessing Plant** (3×3): Consumes scrap per cycle (quantity from recipes.config) and produces higher-level intermediate products. Each product type has a fixed drop probability per cycle, defined in recipes.config.
 - REQ-BLD-11: **Shipyard** (4×2): The player selects a blueprint. Automatically produces one ship of that type whenever all required materials are present in its input buffer. Ship material requirements are defined in ships.config.
-- REQ-BLD-12: **Salvage Bay** (TBD size): A dedicated drop-off point for salvage ships. Scrap delivered here is placed onto connected output belts.
+- REQ-BLD-12: **Salvage Bay** (3×2): A dedicated drop-off point for salvage ships. Scrap delivered here is placed onto connected output belts.
 - REQ-BLD-13: **Belt** (1×1): Transports items. Available in straight and curved variants.
 - REQ-BLD-14: **Splitter** (1×1): Distributes incoming items alternately between two output directions. If one output is blocked, items are sent to the other output until it unblocks.
 
@@ -114,8 +114,41 @@ The following config files drive game parameters:
 
 ## UI
 
-- REQ-UI-1: The elapsed survival time is always visible.
-- REQ-UI-2: The current global building blocks stock is always visible.
-- REQ-UI-3: The player can scroll the view horizontally across the scrollable area.
-- REQ-UI-4: The player can click a building to inspect its current contents and change its selected recipe or blueprint.
-- REQ-UI-5: When clicking a shipyard, the player can also configure stance and target priority for ships produced by that shipyard.
+### Layout
+
+The screen is divided into three vertical sections:
+
+```
++--------------------------------------------------+
+|                  Header Bar                      |
++--------------------------------------------------+
+|                                                  |
+|               Game World (70%)                   |
+|                                                  |
++-------------------------+------------------------+
+| Selected Building Panel | Build Button Grid      |
+|         (left)          |       (right)          |
++-------------------------+------------------------+
+```
+
+- REQ-UI-1: The header bar spans the full width above the game world and always shows the elapsed survival time and the current global building blocks stock.
+- REQ-UI-2: The game world view occupies 70% of the remaining screen height below the header bar.
+- REQ-UI-3: The UI panel occupies the remaining 30% of the screen height, split horizontally into a selected building panel (left) and a build button grid (right).
+
+### Game World
+
+- REQ-UI-4: The player scrolls the view horizontally across the scrollable area by pressing A (scroll left) and D (scroll right).
+
+### Selected Building Panel
+
+- REQ-UI-5: When no building is selected, the panel is empty.
+- REQ-UI-6: When one building is selected, the panel shows: building name, current recipe or blueprint selection, input buffer contents, and output buffer contents.
+- REQ-UI-7: The player selects multiple buildings by box-drag or by Ctrl+clicking individual buildings to add or remove them from the selection.
+- REQ-UI-8: When multiple buildings are selected, the panel shows how many of each building type are selected. No per-building detail is shown.
+- REQ-UI-9: Recipe, blueprint, ship stance, and target priority configuration for a selected building is shown and changed inline within this panel.
+
+### Build Button Grid
+
+- REQ-UI-10: All placeable building types are shown as a flat grid of buttons with no grouping.
+- REQ-UI-11: Each button caption shows the building name and its building block cost, e.g. "Belt: 2 Blocks".
+- REQ-UI-12: Buttons for buildings the player cannot currently afford are shown as disabled.