If the game freezes, just click inside it (games can get unresponsive if you click elsewhere on the page).
Return to the Surface with Brave turtles on this planet.
Press spacebar to jump.
Use the arrow keys to move.
Press Z to launch a focused attack.
Press X to perform a defensive swipe.
Press C to block.
TIP: You gain mutagen when you attack enemies or when you pick up mutagen canisters. When your gauge is full, press X to unleash a special attack.