I can see through the art and the mechanics, that you're a beginner at making games. I liked the idea, but you have a lot to learn. Like, for starters:
- The game didn't have a restart option, if your square disappeared (which, I guess, is losing), then you were just stuck in a room;
- The gun's are too slow, which makes the game very unbalanced;
In order to grow your programming and game design skills, you must also think like the player. Playtest your games as someone playing it for the first time. Other than this, the most obvious tip would be - watch a LOT of game development videos, like TONS OF THEM. I'm pretty sure, I'll be watching them even after 10 years.