This was a fun game! The movement patterns kept things interesting... not too difficult, but not a walk in the park either. I especially liked how the nearly symmetrical levels made me struggle to desync my movements with my clone so that we could both avoid enemies or push boxes without the other undoing a previous push or running into an enemy.
I do wish that the enemies and players interacted with boxes/spikes differently in some cases... having them move through boxes, for example, was strange and sometimes resulted in unexpected box movements. Like sometimes when the box was in a corner I could get on top of it and move it. Sometimes not.
Overall, nice job! The mechanics may be simple, but most of the level design took good advantage of what you built.