You are the spaceship (green thing) and you need to avoid the red circles (and other things) coming towards you. The spaceship follows your pointer because you require extreme agility (it is highly recommended to use a mouse for this). In the top right corner, you have your shield bar which tells you when you are able to use your shield. When it is fully yellow, press spacebar to activate shield. It gives you 5 seconds of invincibility. The shield requires 12 seconds to reload. The game gets harder over time. Good luck!
I got inspired by the original arcade game called Asteroids by Atari. Let me know if you have any more ideas for special circles (like earth, pac man, 8 ball)