There should be self explanatory when you will see this picture. Try to notice what changed in two seconds:
Phew! You failed! I've removed obsidian and replaced it with NPC in spawn menu, since obsidian had no use. So what does NPC actually do? Walks and jumps around. Might sound simple, but he actually learns! He even takes time to learn his moves and mistakes, just like a real human :3.
I've spent hours testing him on my creations, I even called him Garry, poor ol' boy died in a void at the end of the course...
Here's that jumping cockroach:
