Play two falling-block wells at once, the lines you clear upstairs become the obstacles you must survive downstairs.
You actively drop pieces into the TOP well. Every time you clear rows there, the exact gap pattern those rows left is pushed up as garbage into the BOTTOM well. Your efficiency upstairs literally authors the mess downstairs.
Competitive Tetris has always worked by sending garbage: clear lines and the opponent's well rises.
The original idea is to make the opponent yourself. Clears in the top well push their exact gap pattern up as garbage into the bottom one.
That closes a loop the two-player game leaves open. Against a human, efficient play is simply good; here the pattern your clears leave is the mess you will be solving downstairs, so a clean clear and a survivable one are different things.
Shadow Boards reimagines the classic line-clearing block puzzle as a two-front survival act where your success becomes your own obstacle. It's an original, free browser game made in-house at PlayPendium.