I've been playing the WonderSwan version of Raku Jongg so excuse the pic for ants, seems to be a regular port judging from the PS1 videos. It's a mix between a falling block 3+ tile-matcher and Mahjong. It's actually a good mix of both worlds, as it adds an extra element of complexity to a tile-matcher whilst simplifying the regular gameplay of Mahjong and allowing for what normally would be some big hands to be played easily.

To make hands, you just need to get 3 matching suits (in proper ascending/descending order or triplets). If it's not a proper order, the tiles will still be removed and you can still combo to create trash tiles for the opponent, they'll lose if they get to the top as well so you technically don't need to make any hands.

When you do make an almost complete hand, the final double is handled via a "mini-game", this just seems pure chance. If it fails, some tiles will get removed from your hand, but the game continues. If it succeeds you'll get your regular Mahjong score tally.