Ok I’ve been playing it off and on for a week or so and I’ve come a little way since my early what the hell is going on days.
Y is jump which is super counter intuitive but you can get used to it.
There is no damage meter, the percentage under your character is like their chance of going flying when you smack them. So you want your percentage to be small and enemies to be big.
You only score points by smashing an enemy off the stage. (and then they don’t come back on). For some bizarre reason there is no counter telling you how many times you’ve achieved this or been smacked out yourself so you have to keep a mental tally in order to know who is winning.