|Spoiler warning: Plot or ending details follow.|
Go into the door with the stick figure on it. Follow along the path until you see a figure frozen in a cube of ice. Interact with the cube and the Ice effect is yours.
Go into the white door with an eye on it. Go directly up and interact with the pistol.
Go in the green door. Go left and up until you see a yellow and black circle. Interact with it while on top of it. You should be at a place with a mountain-like panorama. Go across it and follow the path in the next area. You should see a staircase leading down. Once you enter the staircase, you should be in an underground sandy area. Interact with the block with a blob on it and the area should light up.
Go back up the ladder you came from and follow the path again and go through the mountain panorama again. You should be in a different room. Interact with the sign at the end and you should be in a brown maze with blue monsters. Go directly right and interact with the speaker to receive the effect.
Go inside the thin plain blue door and navigate the maze until you reach the bottom. You should be in a sandy area with a fast-moving panorama. Go across it and you should be in a place full of gears. Interact with the gear with an eye on it to receive the effect.