A cave animal
Choose one of the animals you see in the cave paintings shown in this video.
Get a piece of paper and a charcoal stick and pin the paper on to the wall of your classroom.
Pause the video at the place where your chosen animal is.
Turn out the room lights (and if necessary lower the blackout) and use just a torch to provide light. That is what it was like when the Stone Age people did it.
Now try to copy your animal. You will be painting on a vertical surface just as people did 30,000 years ago.
Is it easy?