Match your DPS, not your luck
Zone walls happen when average zombie HP out-scalars your deployed team DPS. Push only when your highest-DPS unit can clear a standard zombie in under 2 seconds.
Mind the cooldown cap
Roll Speed upgrades cap at 0.25 seconds per roll. Past that point, additional Roll Speed investments do not translate into more rolls per minute.
Use offline income
Closing the game still pays out Coins and Brains, and the VIP Perk Pass adds +20% on top of that. A short offline stint can fund the next zone unlock.
Rebirth layer math
Each Rebirth layer adds +50% Luck and +100% Coins. Rebirth when the next layer's income multiplier exceeds your current Brains-per-hour yield.