Bullets don't contrast well against the background. As aiming is not easy, I would aim then spam shoot to ensure a bullet hits.
Player movement & turing is good enough to get away from ships quickly, but weaving between them usually results in taking damage. Turning while stationary sometimes has different speeds which was odd. After leading multiple ships, then shooting in a narrow range while stationary can cut down ships quickly in relief.
Escaping can turn into searching for power ups, but as the area becomes busy that usually results in taking damage to collect them.
Ship spawn frequency is high enough that it is better to escape an area than to shoot them all. Some ships spawn too close to the player, giving little time to react. It would be better if there were a larger limit to how close a ship can spawn to the player.
Power up spawn infrequency and sparsity is good as it seems like a decent challenge to collect them while avoiding ships.
It was good to know how much HP was reamining after gradually taking damage. When taking lots of damage back to back it can be confusing to keep track of how much HP was lost. I think I would be more aware of my mistakes if the HP would flash or grow to indicate the instant of lost HP. I thought the HP balancing was decent, by losing 1/2 HP from damage & gaining 1 HP from a power up.
The shake effect on damaged player is nice, but difficult to see when moving. I would have liked the effect to be more intense. The shrink effect on particle from defeated ship is good to indicate a successful shot, which can also notify the user to handle the next ship. I would have liked to see a particle from defeated player. The pulse effect on power ups is good to indicate a point of interest. I thought the variation of animate effects from shaking player, shrinking particles & pulsing power ups is good attention to detail.
I thought the endless scrolling background effect was cool as I always wanted to make one.
The sudden cut from Play to Game Over can give an immediate sense to relax from the keyboard, after being overwhelmed by ships. The score is good to have. I found it a bit arbitrary to not know if I did well or not. The Play Again button is a good way to get back into the game quickly.
Performance of the game seemed to slow down when traveling far, then speed up when defeating lots of ships. Perhaps minimize the processing for far ships by deactivating their hitbox or despawn them.
Object sounds would have been preferred, atleast for power ups as they are a highlight for the player to interact with. Good music choice.