For years, I thought that Taito had made the first competitive block-smashing game in 1997, when they combined Arkanoid and Puzzle Bobble into Puchi Carat. But it turns out that Visco beat them to it by three years when they released Blocken, which for some reason seems to have been totally forgotten and never even got ported to a single home system, despite its ground-breaking concept.
Each match sees the two opponents each smashing blocks in their own seperate well, and the match can end in one of three ways: a player can win by clearing all the blocks in their well, or they can lose by either losing their ball off the bottom of the screen (though each player does start with a row of multi-hit bricks behind them, so this rarely happens) or by having their bat crushed by descending blocks.
It could be said that it's less "pure" than Puchi Carat, though, as while Taito's game uses nothing but blocks, ball, bat and the bottom of the screen to create the rules of engagement, Blocken uses a similar system of power-ups to the infamously brutal SNES competitive puzzler, Tetris Battle Gaiden, in that certain blocks drop stars, which, like the power pellets in TBG, can be saved up and used towards various ends. Using between one and seven stars will push your opponent's blocks down one row for each star used, and if you used more than five, you'll also summon the games mascot, a small winged ball creature, to come and repair one of your protective blocks. If you keep collecting a few more stars after you've saved up seven, your star gauge will start flashing, and cashing in while this is happening gets you all the lesser benefits, as well as a few seconds in a kind of super-mode where your ball smashes through blocks without bouncing off them, and your bat becomes enflamed and indestructible, also destroying blocks it touches.
Once you figure out how the rules of the game work (or have someone explain them, like I just did), it's actually a lot of fun! It doesn't have the aesthetic polish or mechanical purity of Puchi Carat, but it's definitely as fun and totally worth playing. Plus, even without that game's polish, it does have a lot of it's own nice little touches, like how the ball can hit stars on their way down the screen, knocking them slightly off course, or how each of the AI opponents has a slightly different-looking bat. It's little things like that that can really add a lot of character to a simple game like this.
Blocken's a game I definitely recommend seeing out if you enjoy block-smashing games or competitive puzzlers (or both), and it's a shame it never got the attention or recognition it deserves.