An breakdown about theories as to why a game is the way it is. A 25 year old game, which has hit several iterations of game systems, cell phones, not-so modern computers, web browsers, and reinvented with twists, some major, some minor.
I could see an overview of Tetris variants being a three page topic. From Monty Python's bury the bodies where the long straight piece randomly moves, to wild variants, such as Facetris, and Tetris 3-d. I could see the variations on the basics of Tetris itself being about half a page, from the down is an instant drop, up is a turn. It could also feature the form of down speeds up the drop, and two buttons are used to turn in two different directions(clockwise and counterclockwise).
I found the regular mode of Tetris to be mildly interesting, clear 10 lines, pieces go faster, repeat. It leads to a lot of repetition though. The clear X number of lines(25 in the norm I think) with Y number of randomly placed single pieces was more interesting, and provided solid challenges for players of all skill levels.
Of course, the skills you may learn could be fun as well. Planning ahead, logical thinking, space management, and more can be yours with just this one game. Now that I think about it, I can see why Tetris lasted so long.
I guess I could fix it myself, given that it is open source and all... but I'm much more likely to just find some new AAAs for my good old TI-89 and play the real version. 
