Mechanic · enemies & ai · maze

Enemy targeting

How an enemy chooses where to go, such as steering toward a target point the game computes for it.

stubAlso: ghost AI, target tile, chase AI, pursuit AI, scatter and chaseUpdated 2026-10-21
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  2. Games
  3. References
  4. Sources

Enemy targeting is how an enemy picks where to go. In Pac-Man each ghost has its own target tile, set from Pac-Man’s tile, his direction, and in Inky’s case Blinky’s tile1. At each step the ghost takes the open direction closest to its target and never reverses on its own2. Scatter phases send the ghosts to fixed tiles instead3.

  • Target tilePac-Man (1980). Each ghost steers toward its own target tile, picking the move that brings it closest.1,2,3

See also

Mentioned in

Games

GameYearHowNote
Pac-Man1980Target tileeach ghost steers toward its own target tile, picking the move that brings it closest
Every claim about this mechanic, by game (7)
Pac-Man 1980In 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
Mega Man 3 1990Mega Man 3's divide_8bit is Mega Man 2's _divide_mod with its zero-page operands one byte lower ($00-$03 for $01-$04). Its 16-bit division is Mega Man 2's _divide_fraction with its RAM moved and two changes: Mega Man 3 saves and restores X around the loop, and stores the low byte of each successful subtraction back in the remainder ($01), where Mega Man 2 writes it to $09, outside its shift chain.Code
Mega Man 4 1991Mega Man 4's 8-bit and 16-bit division routines, used to aim enemies, are Mega Man 3's divide_8bit and its 16-bit version, byte for byte (103 bytes), at $FC14 in its fixed bank where Mega Man 3 has them at $FCEB.Code
Mega Man 5 1992Mega Man 5's routines for an object's distance to the player on each axis, and the direction to him in 16 steps, are Mega Man 4's, with two changes. It adds two routines that measure the same two distances to another slot's object. And its direction routine starts by setting Y to 0, the player's slot, and falls into the copy of slot Y's position, where Mega Man 4 has a separate entry that copies the player's position and jumps on. The rest is byte for byte, except the address of the 48-byte direction table, which is the same in both and follows the code directly in Mega Man 5.Code
Mega Man 5's 8-bit and 16-bit division routines are Mega Man 4's, which are Mega Man 3's, byte for byte (103 bytes), at $F207 in its fixed bank.Code

References

  1. ^ abIn 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.Codemburkley/pacman-crevised
    How we know
    11479    BLINKY_VECTOR2 = findBestOrientation_2966 (BLINKY_TILE, PACMAN_TILE2, &BLINKY_ORIENTATION);
    pacman.c line 11479 at 3277e56 · upstream ↗
    11525    /*  Make a target tile for pinky that is 4 times pacman's current direction
11526     *  of travel plus pacman's current tile */
⋮
11539    PINKY_VECTOR2 = findBestOrientation_2966 (PINKY_TILE, target, &PINKY_ORIENTATION);
    pacman.c lines 11516–11539 at 3277e56 · upstream ↗
    11584    /*  Inky tries to get pacman in a pincer movement with blinky so he targets
11585     *  a tile that is 2 tiles ahead of pacman's current vector and then twice
11586     *  the vector between that tile and blinky's tile */
⋮
11597    target.y = target.y * 2 - BLINKY_TILE.y;
⋮
11605    target.x = target.x * 2 - BLINKY_TILE.x;
    pacman.c lines 11576–11617 at 3277e56 · upstream ↗
    11637            random:
⋮
11648            XYPOS target = { 0x40, 0x3b };
⋮
11661    uint16_t dist = computeDistance_29ea (PACMAN_TILE2, CLYDE_TILE);
⋮
11669    if (dist < 0x40)
11670        goto random;
⋮
11682        findBestOrientation_2966 (CLYDE_TILE, PACMAN_TILE2, &CLYDE_ORIENTATION);
    pacman.c lines 11637–11682 at 3277e56 · upstream ↗
    12131uint16_t computeDistance_29ea(XYPOS ix, XYPOS iy)
⋮
12139    int b = ix.y - iy.y;
⋮
12152    uint16_t hl = calcSquare_2a12(b);
⋮
12161    b = ix.x - iy.x;
⋮
12178    hl += calcSquare_2a12(b);
    pacman.c lines 12131–12178 at 3277e56 · upstream ↗
    20pacman.6e \
21pacman.6f \
22pacman.6h \
23pacman.6j \
    Makefile lines 20–23 at 3277e56 · upstream ↗

    Checked against the evidence by its author, an AI model, 2026-10-21.

    Revised after a check by a second AI model, 2026-10-21.

    In the claim ledger

  2. ^ abfindBestOrientation_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.Codemburkley/pacman-c
    How we know
    11993XYPOS findBestOrientation_2966 (XYPOS hl, XYPOS de, uint8_t *a)
⋮
12008    OPPOSITE_ORIENTATION = *a ^ 2;
⋮
12014    MIN_DISTANCE_FOUND = 0xffff;
⋮
12032        if (OPPOSITE_ORIENTATION != TRIAL_ORIENTATION)
⋮
12054            /*  If the trial orientation points us at a maze wall then
⋮
12067                uint16_t dist = computeDistance_29ea (DEST_TILE_POS, TMP_RESULT_POS);
⋮
12079                if (MIN_DISTANCE_FOUND >= dist)
⋮
12106    while (++TRIAL_ORIENTATION < 4);
    pacman.c lines 11993–12106 at 3277e56 · upstream ↗

    Checked against the evidence by its author, an AI model, 2026-10-21.

    Checked by a second AI model, 2026-10-21.

    In the claim ledger

  3. ^ abA 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.Codemburkley/pacman-c
    How we know
    4167void ghostsChangeOrientation_0e36 (void)
⋮
4174    if (PACMAN_POWEREDUP)
4175        return;
⋮
4182    if (NONRANDOM_MOVEMENT == 7)
4183        return;
⋮
4191    ORIENTATION_CHANGE_COUNT++;
⋮
4206    if (ORIENTATION_CHANGE_COUNT != DIFFICULTY_TABLE[NONRANDOM_MOVEMENT])
4207        return;
⋮
4214    NONRANDOM_MOVEMENT++;
⋮
4222    BLINKY_ORIENT_CHG_FLAG = 
4223    PINKY_ORIENT_CHG_FLAG = 
4224    INKY_ORIENT_CHG_FLAG = 
⋮
    pacman.c lines 4167–4225 at 3277e56 · upstream ↗
    11434    if ((NONRANDOM_MOVEMENT & 1) == 0)
⋮
11460                XYPOS target = { 0x1d, 0x22 };
11461                BLINKY_VECTOR2 = 
⋮
11479    BLINKY_VECTOR2 = findBestOrientation_2966 (BLINKY_TILE, PACMAN_TILE2, &BLINKY_ORIENTATION);
    pacman.c lines 11434–11479 at 3277e56 · upstream ↗

    Checked against the evidence by its author, an AI model, 2026-10-21.

    Checked by a second AI model, 2026-10-21.

    In the claim ledger

Sources

Code