I am no expert in game development, but I will share some advice I got from someone. When making a plat-former and the player can jump a distance of 5 tiles(or how ever you measure the distance) don't make the gap the player has to jump over 5 tiles wide, make it 4 tiles. This way the player won't get frustrated trying to make pixel perfect jumps.
As for the tutorial maybe you could add the part about bullets giving you a boost. I don't think you should indicate the path to follow, for me discovering the way is part of the fun.
What would be cool though is using the mouse wheel to change colors. This would give the mouse more of a purpose. The first time I played the game I wasn't sure what the mouse was for until I figured out it was for aiming the boost direction.
I hope that helps.