if you want it to work on the website you can try uploading it using version 3.8.2 because that's worked for me. I uploaded an archive of it here: https://archive.org/details/greenfoot-windows-382

Neat game! A few suggestions I have is to make sprites for diagonals so it doesn't flicker when pressing 2 keys and also to lower the goal to something a a bit lower like 25.