I like this a lot. I played through the first dozen or so levels, enough that I'll wait for the final game to play more so they'll be fresh. The grow-and-retract mechanic reminds me of the old arcade game Anteater. I'm curious to see how far you can push the combinations of the various goals and puzzle elements.
My one request/suggestion would be to separate the retract and swap exit buttons. Several times I hammered the retract button to get back to start, but overshot and also moved the worm head. It doesn't seem that both buttons are used, so you could have one button retract and the other move. That would need a bit more audio, some sort of error sound if the player tries to retract when already fully retracted, or tries to move when not fully retracted.
I've bookmarked the project and I'll definitely back for the ROM.