1. Click on the photo of the cat and slide it up.
2. Turn right, click on the spider, it will walk to the bottom of the wall and then walk back up. Now drag the photo of the cat until it’s underneath the spider. Then click the spider again. It will walk on top of the photo. Slide the photo to the right with the spider on top. At the end, the spider will go into the hole and drop a key. Take that key.
3. click under the couch, left side. Take the knife.
4. Look at the rip in the couch and cut it with the knife. Take the key.
5. Look at the safe near the couch, open it with the key from the couch. Take the food.
6. Turn left. Open the safe with the key from the spider. Take the color cartridge.
7. Turn left. Collect the plastic bottles.
8. Turn left. Put a plastic bottle on top of the left machine. Then put the cartridge in the gray opening. Now click on a color button to create a colored tube and take it. Repeat this for every color.
9. Click on the curtains to close them. Then turn around. At the place where you slided the picture up appears a code (which is random). Remember that code and open the curtains again.
10. Turn left. Drag the picture of the cat to the left. Type the code in the text area and push the button beneath it. A hammer falls down. Take it.
11. Reading the “hidden” text on the walls, you should destroy the beast with it.
12. Close the curtains. Pay attention to the numbers. At the right side are the numbers 666. Hit is with the hammer. Take the cartridge. Open the curtains.
13. Put the cartridge in the right machine. Now put some food in the machine and press a color and take the food. Repeat this for all 4 colors.
14. Go to the fishtank (close). Put some food in the tank. Octopussie will eat it and change to the color of the food.
15. Now put the tube from octopussies color in the holder. Octopussie will now jump to the key and open a chest with it. Repeat this for all 4 colors.
16. Hit the back arrow. Click on top op the fishtank. You will now look into the tank from above, 4 numbers will be floating there. This is the code for the door.
17. Go to the device near the door and enter the code.
18. The door is open and you can escape from the room!

using the hammer on the 666 in teh dark

i cant get the code for sliding the picture up with the curtain closed
SPOILER: (click box to reveal/hide)

I slid the picture up. If it's too dark, you may have to brighten your screen a bit.