The major puzzles in the game have a specific icon set:
Reset the puzzle and start again. You will be prompted for confirmation.
SKIP (in EASY mode only)
Solve the puzzle automatically and see the result. Use this only if you are absolutely stuck and do not wish to try again later. The game will prompt you for confirmation; if you click on it by mistake just choose NO to continue.
Leave the puzzle and solve it later. The puzzle will reset when you return.
Puzzles may also have a unique interface. Instructions are provided there.