Drive a ship forward and destroy enemies. When time runs out, game is over. Remaining time is displayed at the left up corner. Remaining time varies according to events:
Ship was destroyed(-15 sec.)
You ship is destroyed when it is hit by a bullet.
Bonus time(+15 sec.)
You can earn bonus time when you reach a certain score. The point you have to get is displayed at the right up corner.
Destroy the boss(+30 or 45 sec.)
The boss enemies appear when you destroy or overtake a certain number(displayed at the left down corner) of enemies, and you can earn bonus time by destroying them.