What do you think of this Tetris variant that is simpler than Tetris?

Here's a prompt to try it out using Gemini 2.5 Pro (preview):

Create a single web page that I can load into a browser that implements this Tetris variant: tetrominoes always retain their shape and are removed in their entirety. In particular, clearing a line would remove all tetrominoes with at least one square in that line. Remaining Tetrominoes do not fall. Use dark mode. Show a shadow.