Your mission in this shoot-em-up game is to defend your base while keeping yourself alive. Be sure to buy weapons and powerups between levels or you will be zombie food.
Use "W", "A", "S", "D" KEYS or ARROW KEYS for movement. Use YOUR MOUSE to aim and shoot. Use your MOUSE WHEEL or "Q" and "E" KEYS to switch weapons. And hit "R" KEY to reload. Good luck!