[Discussion] Specific Pokemon Themed Battles

So for my Fan Game I've wanted to incorporate special battle tournaments where players choose a limited party of Pokemon (ex. 3 Pokemon) but they have to meet certain requirements, such as Pokemon that weigh over 80.00kg or are Ice-Type Pokemon, however I don't know the specific coding towards even the party selections, I was wondering if someone could help me out, it would be greatly appreciated.

Alright side note sorry I realized I should have put this as Question