There are variations on Tetris (e.g. the Tetris Grand Master franchise) where the game mode gets more challenging as you clear. One of the challenges is that th

There are variations on Tetris (e.g. the Tetris Grand Master franchise) where the game mode gets more challenging as you clear. One of the challenges is that the board is invisible, and pieces disappear as soon as you place them; in order to get the best ending, you have to clear a certain number of rows _quickly enough, while still getting tetrises_, while the board is invisible. There are videos on youtube of People doing this. Another interesting one is that it changes all of the blocks to be monochromatic, including in the "Next Block" preview. It turns out that mode is actually more challenging than you might think; at the speed the blocks are dropping, you depend on peripheral vision to tell you what blocks are upcoming, and now you have to actually examine the block to figure out what it is instead of just knowing from the colour.