Add balancing targets section to content_design.md

Record the six root numbers for the balancing pass: run length (win
within ~2 h game time, cycle 20-24), phase boundaries, factory size
curve, fitted threat-cost ladder, swarm fleet size (~25 ships), and
block economy roots (bootstrap, doubling time, expansion cadence).
Derived values are always re-derived from these roots, never patched
directly.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DyCu8vwChKMbLJQ3xosYEN

docs/content_design.md

@@ -171,6 +171,55 @@ It verifies every consumed item has a producer, every item has a visuals
 entry, flags orphaned items, and prints which items are reprocessing-only
 (currently exactly advanced_alloy).
 
+## Balancing targets (first pass, July 2026)
+
+The six root numbers for the balancing pass. Every derived value (threat
+rate, recipe quantities, block costs, scrap rates, unlock ladder) is tuned
+to hit these; when rebalancing later, change these first and re-derive,
+never the other way around. The rules they follow live in
+`docs/progression_design.md`.
+
+All targets are in **game time**. The player can pause and accelerate, so
+real session length differs; playtests should measure both. The time unit
+is the boss cycle (`world.toml boss_countdown_seconds`, 300 s). Destroying
+a station set advances the boss countdown by `boss_advance_seconds`
+(60 s), so cycles run shorter than nominal when pushing actively — these
+targets deliberately ignore that; playtesting will show real run lengths.
+
+1. **Run length** — a winning run takes up to 2 hours of game time: win
+   around boss cycle 20–24. Losing runs end earlier.
+2. **Phase boundaries** — early = cycles 1–5 (iron/copper, small hulls),
+   mid = cycles 6–14 (titanium, medium hulls), late = cycles 15+
+   (advanced alloy, capitals). Push cadence roughly one station set per
+   cycle from mid onward. This fixes the `unlock_at_station_level`
+   ladder and, with the artifact win count, the `artifact_chance_formula`
+   pacing.
+3. **Factory size curve** — producing buildings over time; when
+   saturated, output threat/s equals this count, so this curve IS the
+   player power curve. Targets: ~25 when the starting asteroid is full
+   (end of cycle 2), ~60 at the start of mid (cycle 6), ~120 at the
+   start of late (cycle 15), ~150 near the win. `threat_rate_formula`
+   must remain a fraction of this curve, and buildings plus belts must
+   physically fit the asteroid plus affordable expansions.
+4. **Threat-cost ladder** — total production-seconds per *fitted* hull
+   (including a typical module loadout): drone ~10, frigate ~40,
+   destroyer ~80, cruiser ~200, battlecruiser ~350, battleship ~700,
+   dreadnought/carrier ~1500. Every production chain must sum to its
+   ladder value. Cross-check against (3): fitted-ship cadence =
+   ladder value / (factory threat/s devoted to military) — e.g. a mid
+   factory spending half of 60 threat/s on ships fields a fitted
+   cruiser roughly every 7 s.
+5. **Fleet size** — swarm-leaning: ~25 player combat ships as the
+   standing mid-game fleet. Standing fleet = build cadence (4) × average
+   ship lifetime, so this target drives time-to-kill and therefore the
+   combat stat magnitudes tuned in the arena pass.
+6. **Block economy roots** — bootstrap complete (starting asteroid full)
+   by the end of cycle 2; a factory spending ~30% of its capacity on
+   blocks doubles in ~4 minutes early game; one expansion affordable per
+   cycle at ~1/3 of block income, with escalating costs that eventually
+   outrun any income (see the growth curve rules in
+   `progression_design.md`).
+
 ## Deliberate placeholders / open questions for later passes
 
 - All new hulls have `threat.cost_formula = "0"` so enemy waves do not spawn