the biggest lever is discard strategy. medium and hard bots should track which cards you pick up from the discard pile and avoid feeding cards near those ranks or suits, while dumping high-value deadwood early. they should also judge each draw by how much deadwood it actually removes, and whether it sets up a knock, instead of just counting current melds. the hard bot can guess your hand from your pickups and discards to play defensively. if they're still losing to easy, the bug is probably in the scoring function itself. have it log win-rate per rule so you can see which one is dragging it down.