Visuals are pretty good. I liked the orbital movement mechanical and permanent death. Controls are fine. The issue for me is whenever a celestial body collides with the player, somehow the orbital system mess up its calculations. This happened two times: sometimes when Saturn's asteroids collide with you and the other when the first planet gets a round 2 additive. Orbital system isn't able to calculate a single path rather it is producing multiple and different paths every single frame even without any input.
A minor fixes may require. Overall the game has potential.
Viewing post in Stellar Siege jam comments
I believe you are calculating path every single frame using player's motion vector regardless of W or S input. As a result when some solid object pushes the player away it breaks the system. Alternatively you can bind the calculations to W or S input. Path should only be calculated when W or S is pressed.
1. For the first Saturn fight, when Saturn throw the large asteroid towards player in high velocity. This one is inconsistent to reproduce.
2. When I defeated the Sun, I was pushed back to the first boss. Now it had a celestial machine around him. At that instance, when the celestial machine pushed me into the planet. My orbital path started glitching out. This one is consistent to reproduce.