To be honest, I went into this with low expectations since the premise isn't really anything that sounds too impressive or particularly creative.
HOWEVER, I was pleasantly surprised when I discovered myself having fun with it.
I must praise the use of the first level controlling the snake, since it serves as a good tutorial level to get the basic movement down. It's a good tutorial level because it feels invisible. And that right there is good design.
The game overall is challenging, but has an adequate balance in my opinion. The apples are really useful as a difficulty modulator, since if you find yourself having too much trouble on a level, you can make use of those to give you a bit of an edge to make manageable.
Saving other mice serves as an excellent incentive to push players into tricky situations. And making them optional means that the player can avoid that optional objective if it proves too much for them.
It might be case that the premise isn't something too awe inspiring, but execution of the idea is superb. As long as a prototype goes, this is a good one.
All of that said, the aesthetics could use some love, and the sound kinda gets annoying after a while.
But besides that, it is a pretty solid entry.