Bag Randomizers Create Semi-Predictable Random Sequences
Modern Tetris games use a bag randomizer to select upcoming pieces. Each of the pieces (OSZTLJI) are placed into a bag. Pieces are removed from the bag randomly, one-by-one. When the bag is empty, it is refilled again. Bag randomizers are thus semi-predictable:
- Guarantees an equal distribution of pieces are chosen over time
- Limits worst-case sequences, e.g.,
SZSZ - Limits droughts; there will be at most 12 other pieces between
Ipieces - Limits floods; the same piece will never appear more than twice in a row
The bag randomizer is consistent enough for players to strategize around it, making ST or STZ stacking viable for example.
The New Tetris
The New Tetris rewards 4 × 4 blocks created from 4 tetrominos. If this square is created with 4 of the same tetromino, it becomes a golden square and receives an additional bonus.
It would be difficult to create a golden square with a 7-piece bag randomizer; you’d need a minimum of 16 drops to complete one if you were lucky. The New Tetris uses a 63-piece bag randomizer, with 9 copies of each piece. It’s not uncommon to receive three copies of the same piece within a few drops; a fourth held piece might complete the square.
I love this randomizer. It’s less predictable than the 7-bag randomizer and creates situations that require unorthodox stacking. But it’s still more consistent than an independent randomizer and games can be played for a long time.
Tetris: The Grand Master III: Terror-Instinct
Terror-Instinct uses a hybrid bag randomizer that starts with 35 pieces, 5 copies of each piece. After each draw, the bag is filled with the most droughted piece.
I haven’t played Terror-Instinct enough to have a strong feeling about it. Seems neat.