That's a fun concept, but you might want to speed it up a little bit. I stopped at 20 because I got bored, it's way too slow. The ball moves too slowly and the paddles should shrink a bit faster. The change that occurs between 1 and 20 should probably happen between 1 and 5, or 1 and 3 instead. Edit: oh wait, it's way more fun on Safari. On Firefox it feels slow and slugish, but on Safari it's great!
Hi. I've had the same (good) experience on both. Could it be something in your FF?
And powerups in the middle that make ball bigger or grows one paddle again would be interesting.