It seems that shapes in the official versions of the puzzle game are never truly random: the game tries to avoid delivering the same shape three times in a row. The GB game used a moderately broken routine that incorrectly produced some shapes more frequently than others. Most modern games adopt an approach seemingly inspired by Scrabble, in which all 7 shapes are added to a bag and pulled out at random until the bag is empty. This is a wonderfully simple algorithm, but it sounds like it would lead to horribly predictable games. It also makes it impossible to receive three of a given shape in a row rather than merely very unlikely.
My version of the game started out with a real randomizer (well, as random as you can get with
rand()), but it sometimes made the game unenjoyable - lengthy repetitions of the same unhelpful block, long gaps between shapes I needed, etc - so I tried out the bag idea. Thinking it would be more enjoyable if it were possible to receive the same shape three times in a row I opted to make my bag hold two of each shape. It seems to work pretty well and eliminates the unenjoyable shape sequences, but it does introduce an element of predictability. There’s now a maximum number of shapes that can occur between two appearances of a given shape, which I can use to plan how I structure the playfield.
Worried that this predictability made the game too easy, I sat down for a lengthy play through. I reached level 19 and completed 194 lines. I can’t remember the last time I managed that on the Game Boy. Nuts. I switched to the Game Boy version to see how I did at that. Despite that version now seeming ugly and slow in comparison to my own, I managed to reach level 20 with 201 lines. It’s not easier after all.