Fun prototype. It may be helpful to have a little more consistency in what can be moved (an innate visual cue in the platforms may help with this- maybe using the blue there instead of on the player; you've done a great job making the difference between player and platform clear just by shape/size, so the color could be applied elsewhere) and some restrictions as to how. I wasn't really sure about what the merge mechanic did and didn't need to use it to complete the game.
The music was great, and your visual cues for different parts of the level (player, platform, goal) were very strong, which helps a lot in a mostly two-color environment. :)