First of all, smash all the objects around and build the lift button. Ride up on the lift and use the jetpack to fly over the chasm. Then, walk right as far as you can and find the button to summon an elevator. Ride up and destroy the crates on the left. There is dynamite among them. Use it to destroy the silver block in your way. Destroy the plants in the dome and drill a hole in the ground, using the pneumatic drill. Afterwards, go right and eliminate the opponents.
Use the jetpack to make it over to the right, where there is a color gun swapper with green paint, inside one of the blocks. Fire at the button by the dome. Carry the crate outside and over to the rest of the bricks from one of the crates that you have smashed. You can use them to build a rover.
You need the rover to continue your adventure. Go back and activate the lift by coloring up the two buttons. At the upper floor, enter one of the buildings and use the lever. Then, drive the rover over the bridge and stop on the pressure plate above the chasm.
Moon Base Interior
There is little to do inside the lunar base. Approach the fuse box on the left, by the large robot. Approach the activated panel to activate a minigame. Go left and use color gun swapper, then remove the shield and enter the robot. Approach the active minigame panel. Here, you have to rotate the pipes so that all three points are connected.
After a short cutscene, you will have to fight the final battle. First of all, you will be fighting a robot fight with Rex. Simply, go right and press the action key to pick up the two steel containers and throw them (with the attack key) at Rex. After that, come up to him and start tapping the action key to deal damage to him. You have to repeat that three times.
Afterwards, you will be throwing Rex's people at Rex
The final stage takes place at the shipwreck. You will have to throw opponents at Rex, after you grab them, while he is levitating above the ground. As soon as he lands, he will start chasing you. At that point, you will have to throw a opponent at him and grab him with the action key. Keep doing that until Rex loses all health.
While you are falling down afterwards, you do not have to do much, although you can move around to collect coins in rings. After you leave the ship, while falling, you can collect the Rex Fury coin to the right. Thanks to this, you will be able to perform additional actions during free play.