Series

Pac-Man

5 games, 1980–2021.

Games

Mechanics

Mechanic	Pac-Man 1980
Difficulty ramp	Level table
Enemy targeting	Target tile
Extra life	Once
High score	Single
Kill screen	Draw overflow
Random number generator	ROM as table

A marked cell changed from the game before. “Uses” means the game has the mechanic, with no variant recorded yet.

Every claim, by mechanic and game

Concept	Pac-Man 1980
Difficulty ramp	Each new level advances a pointer one entry along a difficulty table until the entry reads `$14` (20). The DIP switch picks the table: one runs 0, 1, 2, … 20 and reaches 20 on level 21; the other, which the comment calls hard, runs 1, 3, 4, 6, 7, 8, … 17, 20 and reaches 20 on level 16. Each entry selects a 6-byte record at `$0796` that sets, among other things, the movement pattern and the ghosts' counters for leaving the house. Code
Enemy targeting	In chase mode each Pac-Man ghost steers toward its own target tile. Blinky targets Pac-Man's tile. Pinky targets Pac-Man's tile plus 4 times his direction vector, and Inky takes Pac-Man's tile plus twice the vector, doubles it, and subtracts Blinky's tile. The Z80 does both sums as 16-bit adds of a packed two-byte tile and vector (`add hl,hl`, `add hl,de`), so a carry out of the low byte's axis spills into the other axis; away from such a carry, Pinky's target is 4 tiles ahead of Pac-Man and Inky's starts 2 ahead. Clyde targets Pac-Man's tile while the squared distance between them is 64 or more, that is 8 tiles or farther, and otherwise heads for his scatter corner. The translation reads MAME's `pacman` set, Midway's release. Code `findBestOrientation_2966` turns a target into a move: it tries the four directions in turn, skips the reverse of the ghost's current one and any that points into a maze wall, and keeps the one whose next tile has the smallest squared distance to the target; on a tie the later direction wins. Code A mode counter at `$4DC1` runs from 0 to 7: on even values the ghosts head for fixed scatter tiles, on odd values they chase. `ghostsChangeOrientation_0e36` counts time and steps the counter when the count meets a 16-bit entry for the current mode, then flags all four ghosts to reverse. At 7 it stops, so the game holds four scatter phases and leaves the fourth chase phase on for good. The count pauses while Pac-Man is powered up. Code
Extra life	Pac-Man awards one extra life when the score reaches the DIP-switch setting: 10,000, 15,000, or 20,000 points, or never. The table holds BCD thousands (10, 15, 20, and `$FF` for none). After each score change the code compares the score's ten-thousands and thousands digits with the setting, and a flag bit stops a second award. Code
High score	Pac-Man keeps one high score, three BCD bytes at `$4E88`. After every change to a player's score it compares the score with it from the top byte down and, if the score is higher, copies the 3 bytes over and redraws it. Code
Kill screen	The level byte at `$4E13` starts at 0 and gains 1 per level, so on level 256 it holds 255. The routine that draws the fruit row loads it and adds 1, and that `inc a` wraps to 0; 0 passes the "fewer than 8" test, and the draw loop, a `djnz` counted by that 0, makes 256 passes instead of at most 7. Each pass draws a fruit at HL, writes its color `$400` higher, and moves HL on 2 bytes, so from `$4004` the loop steps across about 512 bytes of the 1 KB video RAM at `$4000` and the matching span of color RAM at `$4400`. Code
Random number generator	A frightened ghost picks a random direction from `random_2a23`, which steps a pointer as $p \leftarrow (5 p + 1) mod 8192$ and returns the byte at that address, so the game's own first 8 KB of ROM serve as the random table. The direction is the low 2 bits; a reversal or a wall sends it on to try the next one. Code