Well.. I really liked it. I liked how the colored bricks/keys were not only obstacles but also potentially hazards that could prevent you from winning a level. You had to think before starting each level how you wanted to go about it. It was a good puzzler and I was upset when i found out there were only the 5 levels.
Now, it wasn't all good. The starting screen size is a bit awkward. I had to set my browser to 90% to see the whole play area. You really don't need it to start that large. Second the graphics work and it is a functional game, but it isn't very pretty. When you have a game with a screen this large pretty is important because there is a great deal to look at. In particular the orbs you collect for unlocking blocks look out of place to me. As you continue with this game (and I hope you do) consider the following:
1. All of the ghosts look the same it wouldn't hurt to add some variety. (if the game was much smaller it wouldn't matter as much)
2. The game play works well and your initial level designs are good your next focus should be on making it look pretty and keeping the next groups of levels fun.
3. I liked the music but a mute button is always nice. As it is straight up platform game some sounds wouldn't hurt either.
4. Don't forget to let the player know they are done. Just looping into the final room again isn't the way to go.
5. The game almost begs to have story added to it. Story gives the player a reason to do what they are doing and gives you a way to logically conclude a game that is otherwise just a string of puzzles.
Again really great start, fun and well made. Polish it some and make it longer it is definitely worth the play through. Keep up the good work.