Tetris Worlds

Tetris Worlds was one of the first games to follow the Tetris Guideline.

Like other Guideline games, Tetris Worlds has a relatively long lock delay, a hard drop without lock delay, and full SRS. It shows three next pieces on GBA and five next pieces on other platforms.

Tetris mode
Classic game, albeit with SRS.

Goal of each level L is to earn 5*L points:
 * single: +1 point
 * double: +3 points (2 for lines, 1 for bonus)
 * triple: +5 points (3 for lines, 2 for bonus)
 * tetris: +8 points (4 for lines, 4 for bonus)
 * tetris back-to-back: +11 points (4 for lines, 8 for bonus)
 * T-spin 0 lines: +1 point
 * T-spin single: +3 points
 * T-spin double: +7 points
 * T-spin triple: +6 points

Square mode
Much the same as The New Tetris (which see), except Tetris Worlds has a longer lock delay, no lock delay on hard drop instead of firm drop, full SRS, and (on platforms other than GBA) five next pieces.

Goal of each level L is to earn 10*L points:
 * single: +1 point
 * double: +3 points (2 for lines, 1 for bonus)
 * triple: +5 points (3 for lines, 2 for bonus)
 * tetris: +8 points (4 for lines, 4 for bonus)
 * 4x4 squares: same as in The New Tetris
 * T-spin 0 lines: +1 point
 * T-spin single: +3 points
 * T-spin double: +7 points
 * T-spin triple: +6 points
 * T-spin causes avalanche, just as in The New Tetris, except using SRS T-spin rules
 * extra lines after a T-spin avalanche: not determined

Cascade mode
Nearly identical to the fan game Quadra. After a line is cleared, each tetromino falls as a separate piece under the influence of gravity, and it is possible for pieces to fall and fill in gaps, creating a cascade.

Goal of each level L is to earn 5*L points. The score for each step n of a cascade, where n = 1 to 20, and L lines are cleared:
 * (L + n) * 2 - 3

For example, a tetris-double-single combo scores for a total of 17 points.
 * 1) (4 + 1) * 2 - 3 = 7 on first step
 * 2) (2 + 2) * 2 - 3 = 5 on second step
 * 3) (1 + 3) * 2 - 3 = 5 on third step

Hotline mode
Rows 5, 10, 14, 17, 19, and 20 (counting from the bottom up) are highlighted. Only lines cleared in these rows are counted toward the score.

Goal of each level L is to earn 5*L points:
 * Row 5: 1 point
 * Row 10: 2 points
 * Row 14: 3 points
 * Row 17: 4 points
 * Row 19: 5 points
 * Row 20: 6 points

Sticky mode
Much the same as The Next Tetris. Some tetrominoes are multi-colored and break into smaller pieces of separate colors when they lock. Blocks of the same color glue themselves together; any contiguous group of the same color with 25 or more blocks disappears. Anything with nothing supporting it falls, just as in Cascade mode.

Each level L starts with L + 1 rows of floating garbage on the screen, and the goal of each level is to clear the bottom line of garbage.

Fusion mode
Tetrominoes and single, distinctive "atom" blocks fall. (The ratio is not listed in the manual.)

Clearing a line containing an atom block will remove all blocks in the line except atom blocks, and it will cause a cascade on all lines above the atom block. Each level L starts with L + 1 rows of floating garbage on the screen, and the goal of each level L is to connect 2*L atom blocks to the bottom left corner of the playfield.