claude-home/paper-dynasty/card-evolution-prd/03-tracks.md

3. Evolution Track Design

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3.1 Track Structure

Each evolution track has four tiers (T1 through T4). Each tier contains two to three milestones. Completing all milestones in a tier unlocks the tier's rating boost and advances the card to the next tier automatically. Completing all four tiers achieves Full Evolution.

[Card Acquired]
       |
   [T1: Initiate]  2 milestones --> +small rating boost + visual badge
       |
   [T2: Rising]    2 milestones --> +medium rating boost + embed accent
       |
   [T3: Ascendant] 3 milestones --> +large rating boost + rarity border glow
       |
   [T4: Evolved]   2 milestones --> +capstone boost + full visual rework
                               --> rarity tier upgrade (Standard track, Sta and below)
                               --> card name becomes "[Team]'s Evolved [Player]"

3.2 Track Parameterization

Track definitions are stored in the database, not hardcoded. Each track record specifies:

• Which card type it applies to (batter, starting pitcher, relief pitcher)
• Rating boost amounts per tier (flat probability point deltas, same regardless of rarity)
• Milestone thresholds per tier (admin-tunable)

Tracks are universal — not rarity-gated. A Replacement-level card and a Hall of Fame card follow the same track with the same flat rating deltas. This is intentional:

• Rarity fluctuates during live series. Cards update every 2 weeks during the MLB season. A Reserve card in April could become All-Star by June. Rarity-gated tracks would cause mid-season track jumps, resetting or invalidating progress.
• Flat deltas intentionally favor lower-rarity cards. A +0.5 chances boost to a Replacement card's homerun probability is a larger relative improvement than the same boost to a HoF card. This gives lower-tier cards a reason to exist beyond crafting fodder and avoids making elite cards overpowered.
• Existing rating caps prevent runaway stats. The D20 system has hard caps on individual stat columns (e.g., hold rating caps at -5). Evolution boosts that would exceed a cap are truncated, providing a natural ceiling that prevents creating artificial super-cards.

Three tracks exist at launch (one per card type):

Track	Card Type	T4 Outcome
Batter	All batters	Rarity upgrade (if below HoF) + full visual rework
Starting Pitcher	SP	Rarity upgrade (if below HoF) + full visual rework
Relief Pitcher	RP/CP	Rarity upgrade (if below HoF) + full visual rework

Subtracks are on the table. The schema supports multiple tracks per card type. Before launch, we may add subtracks within each category — e.g., power batter vs contact batter tracks with different milestone compositions, or a closer-specific RP track. The evolution_track table is designed to accommodate this without schema changes; adding a subtrack is just inserting new rows with different milestone sets. The decision on how many subtracks to ship with is deferred until milestone design is finalized.

3.3 Evolution Eligibility

Every card is always eligible. There is no enrollment step, no activation cost, and no slot limit. A card that has not yet reached Full Evolution is always progressing. A fully evolved card (current_tier = 4, all milestones complete) cannot progress further — it has reached its peak state. It can still be crafted (#49) or traded.