Ouch, giving me only a Blastoise with Tackle and three water type moves and an opponent with a Venusaur is just mean. I know those are probably the default moves for a Blastoise at that level but there are plenty of other pokemon to put in the sample battle instead...
I notice that some games on itch.io are able to capture the down arrow key and stop it from scrolling the page (ex.: https://elastiskalinjen.itch.io/oh-high).
I think your suggest would be much better, because the way it's titled right now ("Pokemon prototype game made with JavaScript and p5.js") sounds like it's an official Pokemon project, but it still in the prototype/alpha phase.
Maybe for some inspiration, but to get a really nice metagame (potential to inspired by classic formats like gen 1/2/3), I think it'll be pretty manual to get something fun to play.