Pretty good game, had some interesting mechanics (shrinking/growing).
The level design is pretty frustrating near the end, it's really easy to miss jumps when you are small.
I did find a bug, if you press R while you are holding something it will stay with you. Since you cant' keep the item when shrinking it could make some levels unbeatable without any way to restart the level.
If you are going to make another game, try to add some graphics to the level itself instead of having black blocks everywhere. Having a background is also an instant win graphics-wise.