Awesome game, I would definitely play more levels.
I think that the level should auto-restart, or *press any key* to restart for ease.
The symbols should be explained, for example the save function, I didn't realize what it did until the last level.
Is it possible to soft-lock? Since restarting brings you back to your last save, I was worried about this, but it seems like the levels are designed so you're always making progress and can't get stuck on an island.