*IMPORTANT NOTE* Hold down 'z' not 'x'
Hold down z and repeatedly tap arrow keys to create duplicates. Here are all things that can be created:
- Treadmill: Hold z and tap down->left then let go of z
- Spring: Hold z and tap down then let go of z
- Attack: Hold z and tap right once and then up twice, let go of x after this
Sorry, I didn't realize how confusing this mechanic can be.