Hello, I've decided to build a Tetris framework, and the past days I've been doing some research. Now there's this thing about the vanish zone I don't understand. Why do they use a 24-row playfield? The I is the tallest tetronimo with 4 cells, so having 3 hidden rows should be enough, cause when the tetronimo has no room to appear on the (visible) playfield it's game over. So when is the 24th row used?
Hmm, that's actually not correct. That information was added to the wiki by tepples, the author of Lockjaw, so I assume he knows what he's talking about with regards to that game; but for Tetris Worlds, the playfield is only 22 rows. The tetrominoes are manipulable well above the visible playfield (maybe even in row 255), but anything above row 22 is cut off as soon as the tetromino locks. Regardless, what mufunyo has said is correct; some rotation systems, (most notably SRS), allow climbing. Here's an example: (link) This makes it possible for tetrominoes to be locked in a position much higher than the top of the visible playfield.
Floorkicks and Entry Above Ceiling in Lockjaw come in handy for filling up the full 24. With Entry Above Ceiling, you obviously wouldn't even need to use floorkicks to climb outside first; just fill up 20 rows, get an I-piece, floorkick it, drop it on of columns filled to 20 rows, and you'll have a column filled to 24. However, I guess this will kill you with the default top out rules for Entry Above Ceiling since none of the piece was locked in the visible playfield, haha. So, SRS kicks with Entry Above Ceiling set to off is probably the only way to fill things up and continue your game. Also, I _think_ Tetris DS is confirmed to have a vanish zone of 20 rows. Stack up 20 rows on the left or right side, get 20 rows of garbage, keep an I in hold to facilitate downstacking, and you'll find you still have all of your initial stack once you clear out all the garbage.
From what I rememebr of the source code, LJ does have 4 hidden rows. TDS has at least 15... jujube was the one to demonstrate this, I forget the exact amount.
For single-player play with tetrominoes, 23 rows (20 visible and 3 hidden) are sufficient because of the top out rule. More than that needs garbage enabled: stack high on the left, take garbage, clear the garbage, and see what gets cut off. Full-width garbage (as seen in Tetris Elements Fire and Tetris Friends) doesn't need additional rows of the playfield, as it's really just a lowered ceiling (and is shown as such in Tetris 2 and Wario's Woods). TOD has no vanish zone because like The New Tetris, it uses the Tengen top out rule. But Lockjaw, which uses the guideline top out rule, has 24 rows. LJ65, which also uses the guideline rule, has 23 rows because it uses 256-byte fields divided into 25 rows, and two rows are reserved for the score and lines displays. Maybe it was Elements that had 24. But I remember reading 24 in one of those games' INI files.
