I was about to complain about an impossible situation I came across, but then the side walls destroyed the obstacle and made me go "oooooh, smart", so really props to you for that, a smart "get out of jail free" card on the Design aspect ;>.
The gameplay also works well, does what he has to do and it gives the correct feelings I think.
A thought I shared on some games and that applies to your as well, is that making a trail-and-error heavy level-based game for Ludum Dare can be a double-edged sword. Those who will play your game are 99% of the times other Ludum Dare participants, and we have to play a lot of games, spending no more than 5 or 10 minutes for a game.
Maybe you had a really smart and thought out piece of Level Design at Level 8, but people will never know because they get stuck two times at the beginning of Level 3 after 5 minutes of Gameplay and feel like they saw everything. Probably the hard trial and error was to start around level 9 I think (considering that you said you got to Level 17), with one single frustrating moment around 30 seconds of Gameplay, to establish the mood of the Game and let the player know what experience he or she is going to live.
That being said, I appreciated the game, also that "ooooh" moment was really precious!