The concept of a shoot-em-up based on the idea of time dilation is cool, and it's interesting that it's a 3d view, which is unusual for a spaceship shoot-em-up. However, the thrusters make it play kind of weirdly. Due to the limited ammo and difficulty of aiming, I didn't shoot anything, and I ended up just speeding past everything and into the portal for the first level. For the second level, this did not work, as I often overshot the portal, the spaceship started jerking around, and me frantically trying to bring it back to the portal always ended in it slamming into an asteroid. Of course, I probably shouldn't be trying to bypass all the obstacles by going full speed off the map, but it's pretty difficult to steer the ship between things and there was really nothing preventing me from going full speed off the map, and even if I do properly steer it, I unintentionally end up doing it anyway. The inertia just feels way too overwhelming. Personally, I think it'd be more fun to play if the spaceship was easier to control.
Small note: I think your options menu shows a completion screen instead, not sure what that's about.