The astronaut has a white helmet like head and wears a white suit. He has blue energy like skin and light like eyes. His head is covered in a helmet, which has a visible visor. He has a circular body, with two small feet.
The astronaut lacks arms, and thus cannot arm himself with any weapons. The astronaut travels from planet to planet, jumping with his feet. He has four hearts of health, and dies upon being damaged a fourth time. He is trying to collect all the stars in the level to open a black hole, which he uses to travel to other parts of the galaxy.
He is trying to make his way back home, which seems to be a common theme in Nitrome games.
At the end of the game, he makes it back home. His (what is assumed to be) girlfriend is waiting for him.