pub fn bird_gold_pack(ctx: &RewardCtx<'_>) -> Result<Vec<ESCurrencyUnit>>Expand description
BAL-008/BAL-036: the AD Bird Gold pack — a share of the NEXT chest
upgrade’s price C_(L+1) at the player’s current Chest Level L.
share(L) = 0.6/(13L−10) for 1≤L≤10 (a smooth ≈1/x fit from 20% at L1 to
0.5% at L10), then linear 0.005 − 0.0004×(L−10) down to 0.1% at L20, flat
0.001 past it. raw(L) = round(C_(L+1) × share(L)), and the authored
reward is the monotonic clamp BirdGold(L) = max(BirdGold(L−1), raw(L)) —
the declining share never produces an absolute dip on a Chest Level up.