Still gotta get to the boss yet, maybe when I plug in a controller or something, but I really only have two main complaints at the moment.
First is simple enough, the movement speed might be a touch too sensitive for this type of game, and the second is that having obstacles that require you to shoot through when your gun can overheat feels kind of unfair, especially with how long it takes for the gun to cool down. There aren't too many instances of this type of issue, since there's usually multiple routes you can take, but it does happen a couple times per level it seems.
Overall, it's a fun game with solid mechanics though! Looking forward to trying it with a controller sometime! :)