Use the arrow keys! If you really must, press space to advance a level. However, you only get to skip three times. Finished!!! It only took a month! X3 Every level except the heart is possible. If levels repeat, refreshing should fix that. Or, if you don't care, just do a couple of levels over.
Mostly me, but @Scillog for the engine. I just have to say that this project got more loves in two days than most of the projects I post on @schnubbers get in two weeks. O_o Also do you like the outro?