Heya! I quite enjoy the short time I played this game, so let's go through the positives first:
1) You've definitely got the style nailed down hard here. The simple, minimalistic artstyle with little colours coupled with the simple almost-chiptune music works extremely well. You've done amazingly there!
I have a few qualms about the game but I'll mentioned the most important ones:
1) Controls are a bit hard and finnicky and demands some time to learn. You definitely did implement a grid-based movement, but you need to give more delay between tapping the arrow keys and holding the arrow keys. I find myself easily sliding and gliding along the levels.
2) Overall, somewhat confusing game direction. In my head, I went into this game thinking it was a puzzle game but I kinda got a time-trial-ish game where you have to speedrun to the end. And also the poison-levels were pretty much impossible because your friendly mices would always spawn before you had time to react. I was also unsure at your decision on making the levels randomly generated.
There's a lot to unpack here, but basically what I'm saying is you should considering tightening down your game design direction. Is this a puzzle game? If so, then you can make a score system where you have to complete each level with the least amount of arrows possible. And if you make it a puzzle game, maybe you don't even control a mouse. You just place down the arrows seperately.
I also don't quite understand your initiative at making the levels randomly generated. But I also cannot give a constructive opinion about it so I'll leave it at that.
You've made this game over 13 hours which is nothing to be sad about. At least you finished a game and that's always worth commending!