You need to use your slime hook to maneuver your way around the different mazes. Each level you will have an amount of hooks that you should aim to use. Try not to use any more than the number you are given. You also cannot hook onto anything that isn't either the end box or is green. You can hook to the end box that is black and grey but you cannot hook to the grey walls throughout the levels. You must make sure to not be spotted by any of the guards and you will find that in order to move forward in the levels you will need to kill the guards.