Add player documentation for items, perks, bosses, and gameplay

docs/enemies.md

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+# Enemies
+
+All **6 enemy types** in MeatSlicer, plus elites, drops, and the exact difficulty-scaling formulas. Pulled from `js/enemies.js` and `js/rooms.js`.
+
+---
+
+## Enemy roster
+
+### Shambler
+
+| Stat | Value |
+|---|---|
+| Base HP | 26 |
+| Base speed | 55 |
+| Contact damage | 1 |
+| Hitbox radius | 18 |
+| XP | 1 |
+| First appears | Floor 1 (spawn weight 40) |
+
+The basic chaser. Shuffles toward you with a sinusoidal wobble. Individually harmless, dangerous in the packed waves of later floors.
+
+### Runner
+
+| Stat | Value |
+|---|---|
+| Base HP | 12 |
+| Base speed | 236 |
+| Contact damage | 1 |
+| Hitbox radius | 15 |
+| XP | 1 |
+| First appears | Floor 1 (spawn weight 25) |
+
+Extremely fast, fragile chaser — over 4× the Shambler's speed. They arrive first and force you to keep moving.
+
+### Spitter
+
+| Stat | Value |
+|---|---|
+| Base HP | 20 |
+| Base speed | 60 |
+| Contact damage | 1 |
+| Hitbox radius | 18 |
+| XP | 2 |
+| First appears | Floor 2 (spawn weight 18) |
+
+Ranged kiter. Holds 190–250 px away from you — approaches if you're farther than 250 px, retreats if you're closer than 190 px. Fires a gore bolt (speed 220, damage 1, 3 s life) when within 420 px, every **1.9 s**. Elite Spitters fire a 3-shot fan (0.25 rad spread) every **1.1 s**.
+
+### Splitter
+
+| Stat | Value |
+|---|---|
+| Base HP | 30 |
+| Base speed | 70 |
+| Contact damage | 1 |
+| Hitbox radius | 21 |
+| XP | 1 |
+| First appears | Floor 2 (spawn weight 16) |
+
+Chaser that **splits into 2 Minis on death** (non-elite Splitters only). Slightly tankier than a Shambler. Explosions and AoE that kill the Minis with the parent are valuable here.
+
+### Mini
+
+| Stat | Value |
+|---|---|
+| Base HP | 6 |
+| Base speed | 120 |
+| Contact damage | 1 |
+| Hitbox radius | 10 |
+| XP | 1 |
+| First appears | Only from Splitter deaths and boss summons |
+
+Tiny, quick chaser with a small hitbox. Never spawns directly from room waves.
+
+### Exploder
+
+| Stat | Value |
+|---|---|
+| Base HP | 14 |
+| Base speed | 110 |
+| Contact damage | 2 |
+| Hitbox radius | 16 |
+| XP | 2 |
+| First appears | Floor 3 (spawn weight 14) |
+
+Suicide bomber. Charges at you; within 56 px its **0.5 s fuse** lights (it flashes). When the fuse ends — or when it's killed by anything — it detonates: radius 70 (fuse) / 60 (killed), **2 damage**. The blast only hurts *you*, not other enemies. Kill them at range or bait the fuse and back off.
+
+---
+
+## Spawn weights
+
+| Enemy | Floor 1 | Floor 2 | Floor 3+ |
+|---|---|---|---|
+| Shambler | 40 | 40 | 40 |
+| Runner | 25 | 25 | 25 |
+| Spitter | — | 18 | 18 |
+| Splitter | — | 16 | 16 |
+| Exploder | — | — | 14 |
+
+Weights stay flat once unlocked; floors get harder through stat scaling and wave size, not new mixes.
+
+## Elites
+
+Any wave-spawned enemy can roll as an **elite** (gold ring, HP bar pip):
+
+- Chance: `min(0.03 + floor × 0.02, 0.20)` — 5% on floor 1, capping at 20% from floor 9.
+- **HP ×2.6**, speed ×0.9, contact damage **+1**, radius ×1.45, XP ×3.
+- Drops: 3× XP plus 3–5 bonus gems, **18% + luck×10% chance of an item pedestal drop**, otherwise 60% + luck×20% chance of ammo.
+
+## Drops
+
+| Kill | XP | Other drops |
+|---|---|---|
+| Normal enemy | Its XP value | Ammo: 7% + luck×4% · Heart: 2.2% + luck×3% |
+| Elite | 3× XP + 3–5 bonus | Item: 18% + luck×10% · else ammo: 60% + luck×20% |
+
+Your on-kill items (Volatile Bile, Bloodlust, Vampire Dentures, Dead Man's Switch) trigger off every kill — see [items.md](items.md).
+
+---
+
+## Difficulty scaling
+
+Every enemy's stats are computed at **spawn time** from three factors: floor, your power score, and pressure.
+
+**Power score** = `(your level − 1) × 0.5 + (sum of all your item tiers)`
+
+**HP:**
+```
+base HP × (1 + 0.22 × (floor − 1)) × (1 + 0.05 × power) × (elite ? 2.6 : 1) × pressure
+```
+
+**Speed:**
+```
+base speed × (1 + 0.04 × (floor − 1) + 0.01 × power) × (elite ? 0.9 : 1) × rand(0.9, 1.1) × pressure
+```
+
+**Contact damage:** flat per type (elites +1) — it **never scales with floor**. What kills you late-game is volume, speed, and HP pools, not bigger hit numbers.
+
+**Pressure** (see [gameplay.md](gameplay.md#pressure-dynamic-difficulty)) ranges 0.75–1.60 and multiplies both HP and speed. Playing flawlessly pushes it up; getting hit pulls it down.
+
+### Example: Floor 10 Shambler
+
+Level 8 player (3.5 power) with 8 item tiers (8 power) → power 11.5, pressure 1.2:
+
+```
+HP:  26 × (1 + 0.22×9) × (1 + 0.05×11.5) × 1.2  =  26 × 2.98 × 1.575 × 1.2  ≈ 146
+Spd: 55 × (1 + 0.04×9 + 0.01×11.5) × 1.2          ≈ 55 × 1.475 × 1.2          ≈ 97
+```
+
+vs. 26 HP / 55 speed on floor 1. Build damage accordingly.
+
+## Wave sizes
+
+Combat rooms spawn `3 + ceil(floor × 1.4)` enemies in wave 1, plus a second wave (×0.7) from floor 2 and a third (×0.5) from floor 4. Full table in [gameplay.md](gameplay.md#waves-per-combat-room). Hard cap: 72 enemies alive at once.