So far I've played the first 5-6 levels on Kongregate in two separate visits, thanks to your online system for remembering my last completed level. The game plays smoothly and without any errors or glitches. Here are some thoughts:
Gameplay
The good news is that the gameplay feels very familiar. After a short intro story, I was able to begin playing immediately, without any confusion about the game's objective or how the controls worked.
The bad news is that the gameplay feels very familiar. The first 4 levels or so felt nearly identical. Pretty much the same difficulty, the same challenge of pressing the button to open doors, and the same challenge of shooting those bug-eyed mice creatures. So I lost interest and stopped playing.
But after looking more closely at the screenshots here, I decided the higher levels might offer something different. So I played a few more levels. And yes, the challenges became a bit more varied. So I suppose my main suggestion is to offer players some glimpse of variety earlier in the game. Otherwise, you risk losing players after a few levels because they think the game is too repetitious.
In terms of detail, this is fairly good. The controls are smooth and intuitive, they work for both left- and right-handed players, and they need no explanation. Likewise, completing each level seems intuitive: press button to open door, dodge or kill the attacking mice, avoid the cannon shots, and get to the next portal. Hopefully, the higher levels will offer more challenging puzzles.
Graphics
The graphical style is good enough. Nothing really unexpected -- mostly circle and square shapes with neutral colors. It's a style one sees a lot these days, but there's nothing wrong with it. Frankly, I'd rather play a game with this style, than with a highly pixelated style where objects are barely recognizable. My only suggestion would be to consider ways to add some sense of depth. Maybe a little background shading to suggest lighting? Maybe some shadows to give a sense of mood? Nothing dynamic, necessarily. Just something to break the sense of flatness and uniformity.
Sound
The soundscape is OK. But the game could use some work here. Other than the shots and the few explosions, there's not much going on aurally. You could add door sounds, and maybe some background themes. And those bug-eyed mice could make some sounds with they attack and feast on your dead body.
Overall
I enjoyed this. It is fairly well made. And the automatic level-save system makes it easy to resume gameplay. Nothing really jumps out at me as imaginative or out of the ordinary. But the gameplay is solid and entertaining. So I'm planning to play a few more levels. And I'd recommend this to others.