Feraligatr moves with the arrow keys. Charizard moves with the WASD keys. When you click Feraligatr it flashes with colors. When you click Charizard it flashes with colors.
You can click the See inside button and switch the background to just the Charizard one or just the Feraligatr one. I personally like Feraligatr more than Charizard. If you would like to tell me who you like more you can put it in the comments.
