The instructions are a bit hard to follow just with text. It might be easier to follow if they were somehow embedded into aspects of play. It was also a bit tricky to get a hang of the controls (it was unclear what the shoot button was - I had to experiment a bit to figure it out). The first level is simple enough that you do have some room to play around before you start digging into the more challenging stuff.
I like the overall idea of the mechanics of the game. It feels like there's generally a solid difficulty ramp. Some aspects of the controls feel like they could maybe be adjusted? Having to move in the direction that you want to shoot the gem feels a little awkward sometimes. I could just be bad at games though - very possible :P
It didn't feel like there was enough of an incentive to shoot gems into the spawner. Because there's no time pressure and the homing enemies all collapse into each other - it's easier to just ride it out and collect the gems slowly. Adding some more kinds of pressure might help?
Amazing visuals. Great music. Good sound effects.
Overall, really solid game!