This is a great game, I've played through it multiple times
I think I crashed the browser version of game, here are the steps that it took
- Have the move copy
- Encounter an enemy with the move stop
- The enemy uses stop
- Use the move copy on the next turn to replace one of the enemy's move with go
- The turn after the enemy uses go to regain their move, use copy to copy go
- The screen turned black
Edit: refreshing the page brought me back to the beginning of the level