How the Pac-Man Ghosts Decide Where to Chase You

You clear the first board of Pac-Man, feel good about it, and then on the second board the red ghost seems to read your mind. You duck into a side corridor and the pink one is already waiting at the other end. It feels like the machine is cheating, or at least improvising, and most people who play the game casually give up on learning it because of that feeling.

It is neither. The 1980 arcade original runs four small, fixed rules, one per ghost, and once you can see them the "mind reading" turns into something you can plan around. I spent a long weekend with an original cabinet at a friend's bar and a frame stepping emulator, checking the rules people quote online against what the ghosts actually do, and nearly all of it held up. Here is the version I wish someone had handed me twenty years ago.

Every ghost is chasing a single tile, not you

The maze is a grid of 28 by 31 tiles. A ghost never looks at the whole map and never plans a route. It only makes a decision when it reaches an intersection, and the decision is crude: of the tiles it can step into next, pick the one with the shortest straight line distance to its target tile. It is not allowed to turn around. If two options tie, it prefers up, then left, then down, then right.

That last detail sounds trivial, but it explains a lot of the strange loops you see. A ghost whose target sits behind a wall will happily take a long detour, because a straight line through the wall looks short from its point of view. It has no concept of dead ends, just "which neighbouring square is closer to where I want to be."

So the real question is where each ghost places its target. That is the part that differs, and it is why the four of them feel like four personalities.

The four targets, side by side

The Japanese release names hint at the design. Blinky was Oikake (roughly "chaser"), Pinky was Machibuse ("ambusher"), Inky was Kimagure ("fickle") and Clyde was Otoboke ("playing dumb"). Those names match the targeting code almost exactly.

Inky deserves a closer look because his rule is the clever one. Take the tile two spaces in front of Pac-Man. Draw a line from Blinky to that tile, then double its length. The end of that doubled line is Inky's target. When Blinky is close behind you, Inky ends up near you too. When Blinky is far away, Inky's target flies off across the board, which is why he sometimes ignores you completely for ten seconds and then appears from nowhere.

Clyde's switch at 8 tiles is the reason he seems shy. He charges until he gets close, his target flips to the bottom left corner, he turns away, gets far enough to switch back, and charges again. If you spend a lot of time in the lower left quadrant, though, his corner and your position overlap, and the shy ghost becomes a very real problem.

The upward bug that everyone forgets

There is an overflow error in the original code. When Pac-Man faces up, "four tiles ahead" for Pinky becomes four tiles up and four tiles to the left. The same glitch shifts Inky's reference point two up and two left. In practice this means Pinky is weaker than she should be when you are moving upward, and you can sometimes walk straight toward her without her committing to a block.

The clock that runs underneath everything

The ghosts do not chase all the time. On the first level they alternate between scatter and chase on a fixed timer: 7 seconds of scatter, 20 of chase, 7 of scatter, 20 of chase, 5 of scatter, 20 of chase, 5 of scatter, then chase for the rest of the board. In scatter mode each ghost heads to its home corner and circles a small loop there.

Levels 2 to 4 shorten the last scatter phase to a single frame and stretch the third chase phase to 1,033 seconds, and from level 5 onward the scatter windows are all 5 seconds. The practical upshot is simple. Your breathing room is front loaded. The first 30 seconds of a board are the safest you will get, so that is when to clear the dots in the most awkward corridors.

Every time the mode changes, every ghost reverses direction on the spot. Experienced players watch for that sudden about turn because it tells you the timer just ticked, even when nothing on screen announces it.

The game never tells you which mode it is in. The ghosts do, if you watch them turn around.

Frightened mode, after you eat an energizer, pauses that clock rather than resetting it. On level 1 the blue phase lasts about 6 seconds, and the ghosts pick turns using a pseudo random number at each intersection instead of a target. Eating them in sequence pays 200, 400, 800 and 1,600 points.

The advice that does not hold up

The most repeated tip I hear is "keep moving and the ghosts can never catch you." It is half true at best. On level 1 Pac-Man runs at 80 percent of the game's top speed and the ghosts at 75 percent, so on paper you are faster. But Pac-Man stops for one frame on every dot he eats and three frames on an energizer. In a corridor full of dots you are effectively slower than Blinky, and that is exactly where people get caught.

The fix is not to move more. It is to eat dots while running away from nothing, and to run through already cleared corridors when something is behind you. Empty lanes are your escape routes, so clearing the board in a sensible order matters more than speed.

Blinky also has an extra trick the casual tip ignores. When the number of dots left on the board drops low (20 on the first level), he speeds up, and at 10 dots he speeds up again. Fans call this "Cruise Elroy." In that state he keeps chasing even during scatter. Leaving a handful of scattered dots in far corners is the single most common way I see a good run fall apart.

Small habits that use the rules against them

Four spots on the board, the two intersections just above the ghost house and the two just above Pac-Man's starting position, do not let ghosts turn upward during chase or scatter. Players call them the red zones. If you go up through one of those junctions with a ghost behind you, it is forced to continue sideways, and you buy a second or two.

The side tunnels are the other gift. Ghosts slow to roughly 40 percent speed inside them while Pac-Man does not, so a tunnel trip is a real way to shake Blinky late in a board.

And when Pinky sits in front of you and you are moving toward her, you can often turn toward her rather than away. Her target is four tiles ahead of you, so as you approach, her target moves behind her, and she may peel off before you meet. It feels reckless the first time. It works more often than not, though I have lost enough lives to it that I would not call it safe.

If any of this makes you curious about why old games reward this kind of study, we wrote about what makes a retro game worth replaying, and the broader question of which arcade genres still hold up.

One thing to try this week

Play three games of Pac-Man, on whatever version you have access to, and ignore your score. On each one, watch only for the moment all four ghosts turn around at once, and count the seconds between those turns on the first board. Once you have seen the 7, 20, 7, 20 rhythm with your own eyes, the game stops feeling random, and you will start saving the hard corridors for the opening scatter. There is more where this came from in our retro and arcade section.