Keeper Slots

Adds a new green slot. Sushi in these are NOT taken away when resetting, but are subject to a -3 tier reduction.

Upgrade Details

Field	Value
Cost growth	50x per level before New Game+ adjustment
Cost behavior	Normal room upgrade. Room cost reductions can apply; New Game+ makes cost growth steeper.
Player impact	Improves the room’s income, speed, cost curve, or support systems.