Build your towers on the green area before the time runs out. Then launch the round and hope you survive longer than your opponent! Your towers only destroy the enemies of opposite colour, which attempt to exit through your gate.

Keyboard shortcuts (HOLD SHIFT TO USE):
Escape: Deselect
S: Sell
U: Upgrade
1: Build Debris Tower
2: Build Laser Tower
3: Build Missile Tower
4: Build Shockwave Tower
5: Build Frost Tower
6: Build Anti-Air Tower