Thanks for the kind words! Yeah, if I expanded this into a full-fledged game, I have a lot of ideas to expand on the variety in each world or even just the gameplay in general. I'd still love to keep it mostly simplistic, but I'd like some mechanic or gimmick in each world to spice things up a bit.
As for the high scores, you should just be able to use the arrow keys to select a letter, then press X to confirm that letter. Start will take you to the enter symbol in the bottom right corner. Just press X on that and you'll confirm your name. If that doesn't work, hmmm... maybe there's a weird issue?