Move as far right as you can, then go up collecting the crystal below a spider. Head down, breaking some earth and collecting a crystal, then move up. A rock should fall on the spider.
Move left until you're next to the bouncy ball, (Not the one in the bottom - left of the level,) then head up until you can't move any further. Move right, dropping the rock on the spider.
Go to the bit above the room the blue player's in. There are three rocks, one to the left of the entrance, one to the right and one two spaces above the entrance. Move this rock right twice.
With the blue player, move up once to let the rocks drop. Move left then up, so you're out of the room you started in.
With either player, collect the crystal to the left of the mirror below the bouncy ball. (The one in the middle of the level, not the bottom - right.) Collect the earth above this mirror, and move to get out of the way onf the bouncy ball. Wait for it to fill the hole.
(Blue player) Clear all the earth and crystals (but not the key) on the furthest - left part of the level. Avoid the spider.
Go to the middle of the level then go to one space above the mirror there. Go directly upwards until you're right of the crystals under the rocks, then keep going left then up once, then left, dropping the rock onto the spider. All the spiders have now been killed. Collect the silver key.
With either player, go to one space left of the rock keeping the sticky ball trapped. Move this rock left, then move out of the way.
(Optional) Clear the earth to the top and right of the mirror in the bottom - left of the level where the bouncy ball is. This should hit the sticky ball, making it take a different wall, and fall into a hole.