5 click upgrades, each linked to a generator type:
- Nid Douillet (+1/clic, 50 base) — requires owning a Nid
- Eau Fertile (+3/clic, 500 base) — requires a Mare
- Spores Actives (+8/clic, 5k base) — requires a Marecage
- Courant Vital (+20/clic, 50k base) — requires an Etang
- Source Ancestrale (+50/clic, 500k base) — requires a Lac
Cost scales x1.2 per level. Reset at prestige (like generators).
Click gain = (base + upgradePower) × prestige × tree × infraBonus.
ClickPanel shows upgrade shop with level badges and gen requirements.
Adds tadpole sink for active play — strategic choice vs buying generators.
Server saves don't store all node fields (branch, cost, effect, etc.).
migrateSave now always rebuilds tree from DEFAULT_EVOLUTION_TREE,
preserving unlocked state from the save. Fixes empty evolution tree.