first of all, thank you for linux build!
the game is amazing, i have not beat the game yet, but i love solving this kind of puzzles so much that i would love to buy some kind of expanded version.
i don't know why, but the game reminds me of 'rochard' game, i think this kind of plot would fit your game perfectly.
also it would be nice, if lava inside the tube will look darker, so it could be more clear, which tube is yellow one.