A/D - move
Space  - jump
Mouse - aim
LMB - shoot.

You are an astronaut who got into an accident and fell on an unknown planet. There are malevolent creatures here. You need to repair your spaceship and return to your planet.

In the right top corner there is the time that needed to repair your spaceship. In the upper center is the time of the current wave, the remaining time after each wave will be subtracted from the time to repair (you have free time left after the wave and you spent it on repairing the ship). If you don't clear a wave on time, the extra time you spent will be added to the time  to repair. If the enemies reach the ship, time to repair will be increased, as they have caused damage to the spaceship.

All this should have been clear during the game, but I didn't have time to do it, so I just wrote it here :)