Energy economy — action fuel + tight budget
D-018: Energy economy — action fuel + tight budget
Picks 1 + 5 from the 2026-05-21 vision verification session. D-007 §2 canonised the Energy input (1 step = 1 Energy + streak bonus; +20% at 7d, +50% at 30d). The spend side was unscoped — every mechanics surface negotiated its own cost shape independently, and D-016’s removal of XP left Energy without a defined non-progression role. D-018 closes both gaps: one fungible resource, four canonical sinks, tight budget.
Decision (the four canonical sinks):
| Sink | Cost shape (% of nominal 5k-step day) | Notes |
|---|---|---|
| Combat encounter | ~30% per fight (premium) | Resolution per D-010; encounter selection model in forthcoming D-decision (pick 6 — pull-based queue + difficulty-tiered pool). |
| Craft attempt | ~20% per attempt | Affix re-roll (W-level under mechanics-designer; pick 8 demoted out of D-flow). |
| Tree allocation | ~10% per node | Allocating an already-unlocked passive. Quest-point unlocks (D-016) remain free; the commitment costs Energy. |
| Leak harvest | variable, exposure-tied per D-014 §3 | Already canonical; D-018 confirms Energy as the sink. |
Daily budget reference (canonical envelope):
A nominal 5,000-step day (no streak bonus = 5,000 Energy) yields one of:
- 2-3 combat encounters (at 3 fights, no meaningful headroom for craft/alloc; at 2, ~40% slack — one craft attempt or two allocations)
- ~5 craft attempts (no combat that day)
- ~10 tree allocations (no combat, no craft)
- mixed plays at lower counts each
Streak bonus per D-007 §2 inflates this envelope proportionally. A 30-day-streak walker at 5k steps has 7,500 Energy — still tight relative to the action menu.
Design intent:
Force-choice scarcity. A walker cannot do everything in a single day. Each session is a triage: fight today, craft today, or commit to the tree today. PoE-style scarcity discipline. This is the canonical translation of D-001 (full product, hardcore audience) and D-008 (premium positioning).
What D-018 does NOT decide (delegated):
- Per-encounter damage cost variance — B-level (mechanics-designer).
- Specific craft re-roll formula — W-level (mechanics-designer, pick 8).
- “Today’s budget” UI surface — ui-designer call.
- Energy day-rollover policy (carryover vs reset) — W/B-level under mechanics-designer, constrained to: carryover ≤ 1× nominal daily budget. Unlimited hoarding would break the force-choice scarcity D-018 anchors; the ceiling preserves it while leaving the shape (linear decay vs hard cap vs none) open.
- Energy ledger schema + sink-debit endpoint design — tech-architect spec; backend-engineer implements per spec (Phase 13+). Touches D-007 §3 anti-cheat reconciliation — sink debits must be server-authoritative.
Rejected alternatives:
- Per-action separate currencies (combat tokens, craft tokens, alloc tokens) — fragments Pillar 1, abstracts the walk-to-action link, makes “I walked 5k today” stop being legible.
- Generous budget (5k steps ≈ ~10 combats + craft + alloc) — kills choice tension, makes streaks meaningless, contradicts D-008 hardcore positioning.
- Combat-only sink — leaves craft / allocation / harvest energy-free, fragments the resource model in the opposite direction.
Reasoning:
Pillar 1 (Steps = Energy) had a defined input but no defined spend. Without D-018, every mechanics surface that consumed Energy negotiated its own cost shape, risking either trivialisation (everything cheap → walking is friction-free → no choice) or grind (everything expensive → walking is a chore). Tight budget + premium combat anchors the hardcore PoE feel D-008 sells the product on. The four-sink table is deliberately small — adding a fifth sink (e.g. fast-travel, NPC bribe) requires a new D-decision, not a B-level extension.
Source: picks 1 + 5 from ops/memory/vision-qa-2026-05-21.md. Triage by game-director recorded inline at /decide ratification (2026-05-21 session).