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+# TODO
+
+## Ascension Buff Tree — Needs Review Before Implementation
+
+### Goal
+
+Add a permanent buff tree system:
+- **Separate** from existing `GeneratorBuffData` (which resets on prestige).
+- **Permanent** — prestige does NOT reset ascension buff state.
+- **Unlocked** by spending ascension currency (earned during prestige).
+- **Tree/DAG-structured** — nodes have prerequisites (parent_ids) that must be met before a node can be purchased.
+- **Multi-level** — nodes can be one-shot unlocks (`max_level=1`) or repeatable upgrades (`max_level>1` or `-1` for infinite).
+
+### Data Structure
+
+#### `AscensionBuffNode` (Resource)
+Single node in the tree.
+
+| Field | Type | Notes |
+|-------|------|-------|
+| `id` | `StringName` | Unique node ID |
+| `display_name` | `String` | UI label |
+| `description` | `String` (multiline) | Tooltip |
+| `icon` | `Texture2D` | Visual |
+| `parent_ids` | `Array[StringName]` | Prerequisites (DAG, not strict tree — multiple parents allowed) |
+| `effect_type` | `enum EffectType` | What this buff does |
+| `effect_value` | `float` | Base effect magnitude |
+| `effect_per_level` | `float` | Extra effect per level beyond first (default 0.0) |
+| `target_id` | `StringName` | Target generator/currency for type-specific effects (empty = global) |
+| `cost_mantissa` | `float` | Ascension currency cost base |
+| `cost_exponent` | `int` | |
+| `cost_multiplier` | `float` | Cost scaling per level |
+| `max_level` | `int` | How many times it can be upgraded (1 = one-time, -1 = infinite) |
+| `tier` | `int` | Row in tree UI (visual grouping) |
+| `x_position` | `float` | Column in tree UI |
+
+**Effect types** (extensible enum):
+
+```
+GLOBAL_PRODUCTION_MULTIPLIER      → multiply all generator output
+GENERATOR_PRODUCTION_MULTIPLIER   → multiply one generator's output
+CURRENCY_PER_RUN                  → start each prestige with this currency
+COST_REDUCTION                    → reduce all generator purchase costs
+PRESTIGE_GAIN_MULTIPLIER          → earn more ascension currency per prestige
+GENERATOR_COUNT_MULTIPLIER        → scaling based on owned generator count
+RESEARCH_XP_MULTIPLIER            → faster research leveling
+```
+
+#### `AscensionBuffCatalogue` (Resource)
+Flat list of nodes. The tree emerges from `parent_ids`. Follows existing catalogue pattern (`BuffCatalogue`, `GoalCatalogue`, etc.).
+
+| Field | Type |
+|-------|------|
+| `nodes` | `Array[AscensionBuffNode]` |
+
+#### State in `LevelGameState`
+
+```gdscript
+@export var ascension_buff_catalogue: AscensionBuffCatalogue
+var _ascension_buff_levels: Dictionary = {}  # {StringName: int} — node_id → unlock count
+```
+
+- Never cleared by `reset_for_prestige()` (unlike `_buff_levels` for generator buffs, which IS cleared).
+- Normalized/sanitized on load (like generator states).
+
+### Save Format
+
+- Bump `CURRENT_SAVE_FORMAT_VERSION` from 7 → 8.
+- New key: `"ascension_buff_levels"` → `{ "node_id": level_int, ... }`.
+
+### API on LevelGameState
+
+| Method | Purpose |
+|--------|---------|
+| `purchase_ascension_buff(buff_id) → bool` | Spend ascension currency, increment level, emit signal, save |
+| `can_purchase_ascension_buff(buff_id) → bool` | All parent_ids met? Under max_level? Enough currency? |
+| `get_ascension_buff_cost(buff_id) → BigNumber` | Cost for the NEXT level (scaled by `cost_multiplier`) |
+| `get_ascension_buff_level(buff_id) → int` | Current unlock count |
+| `get_ascension_buff_multiplier(effect_type, target_id) → float` | Walk tree, compute combined effect |
+| `get_available_ascension_buffs() → Array[AscensionBuffNode]` | Nodes with prerequisites met |
+
+### Signals
+
+```gdscript
+signal ascension_buff_changed(buff_id: StringName, new_level: int)
+signal ascension_currency_changed(new_unspent: BigNumber)
+```
+
+### Prestige Integration
+
+No changes needed to `PrestigeManager._reset_all_buff_levels()` — it only touches `_buff_levels` (generator buffs), not `_ascension_buff_levels`. The new dictionary naturally survives the reset.
+
+### Purchase Flow
+
+```
+Player clicks upgrade node
+  → can_purchase_ascension_buff(node_id)
+    → All parent_ids at required level?  (max_level for prerequisite, or just ≥1)
+    → Current level < max_level?
+    → Enough ascension currency?
+  → YES: spend_currency_by_id(ascension_currency, cost)
+  → _ascension_buff_levels[node_id] += 1
+  → emit ascension_buff_changed
+  → save_game()
+```
+
+### Example Tree Content (Illustrative)
+
+```
+Tier 0 (roots):
+  strong_start          → +10 gold/run           cost: 1   parents: []
+  efficiency            → +10% global prod       cost: 1   parents: []
+  thrifty               → -5% gen costs          cost: 2   parents: []
+
+Tier 1:
+  better_start          → +100 gold/run          cost: 3   parents: [strong_start]
+  enhanced_efficiency   → +25% global prod       cost: 3   parents: [efficiency]
+  double_dip            → +50% gold from forestry cost: 5   parents: [strong_start, efficiency]
+
+Tier 2:
+  power_surge           → +100% global prod      cost: 10  parents: [better_start, enhanced_efficiency]
+```
+
+### Files to Create/Modify
+
+| File | Action | Purpose |
+|------|--------|---------|
+| `core/ascension/ascension_buff_node.gd` | Create | Node resource |
+| `core/ascension/ascension_buff_catalogue.gd` | Create | Catalogue resource |
+| `core/ascension/ascension_buff_tree_panel.gd` | Create | UI panel (or integrate into prestige panel) |
+| `core/level_game_state.gd` | Modify | Add catalogue ref, `_ascension_buff_levels`, purchase/query methods, save/load, signals |
+| `core/prestige/prestige_manager.gd` | Modify (light) | Emit `ascension_currency_changed` on spend/earn |
+| `docs/gyms/tiny_sword/ascension/*.tres` | Create | `.tres` resources for actual tree content |
+
+### Open Questions for Review
+
+1. **Prerequisite level requirement**: Should a parent need to be at `max_level`, or is level 1 sufficient? (Leaning: `max_level` is required, otherwise the tree loses structural meaning.)
+2. **Effect stacking**: For `GLOBAL_PRODUCTION_MULTIPLIER`, should separate nodes multiply together or add? (Leaning: multiply — consistent with the existing generator buff multiplier pattern.)
+3. **UI placement**: Should the tree panel be a tab in the prestige panel, a separate screen, or inlined somewhere?
+4. **Ascension currency unspent tracking**: Currently `PrestigeManager.current_prestige_unspent` tracks unspent prestige currency. Should the buff tree consume from this directly, or should ascension currency be a proper `Currency` in the catalogue that the tree spends via `LevelGameState.spend_currency_by_id()`? (Leaning: use `spend_currency_by_id()` for consistency — ascension currency is already added to the currency catalogue.)
+5. **Content**: What actual buffs and tree shape should the first version ship with?