Google celebrated the 30th anniversary of Namco's classic arcade game Pac-Man today with the first ever interactive doodle header on its main page. The doodle adapts the original version of Pac-Man to a new layout that spells out "Google," with the ghosts' monster box forming the second "G." The "I'm feeling lucky" button has been replaced today with "Insert Coin," and clicking it takes you into the game (two-player Ms. Pac-Man is also available if you click the button twice). The game uses a deterministic AI as does the original Pac-Man, but with a few twists, and given the totally new layout, this has some interesting effects upon gameplay.
As for the basic layout, there appear to be roughly the same number of dots, but there's no symmetry, and one power pellet is added inside the first "G." Both Pac-Man and the ghosts spawn slightly right of middle in the level. Perhaps most importantly, the level itself is much wider than it is tall, which means the side gates that wrap to the other end of the level get much less traffic. This is one of several measures taken to make the player's job a little tougher this time around.
The original programming of Pac-Man was rather vulnerable to exploits with six people have gotten perfect scores (it isn't easy, but it can be done). Because the ghost AI is entirely deterministic and based on the position of Pac-Man, the player technically controls where they go. Therefore, patterns were eventually developed that, if memorized and followed perfectly, made certain the player would not die. A different bug of sorts allowed players to move straight through ghosts without dying if they were lucky, because of the way the game detects collisions.
This version of the game still contains the latter bug — I've still come away safe twice when going straight for the ghost — and the ghost AI is only barely different. If you ever thought that the ghosts all seemed to have a character of their own, you weren't too far off. Each ghost uses a different deterministic AI based on the position of Pac-Man and the direction of the player's joystick. The pink ghost goes directly for Pac-Man, the red one goes fast and tries to cut him off (uses your joystick data to guess which way you're going), the orange one tries to keep his distance from Pac-Man, and the cyan ghost is slow and meek, but can suddenly adopt any of the other AIs at seemingly random times.
At specific time intervals, the ghosts switch away from that AI to simply go toward their corner, usually giving the player some time to breathe so long as he doesn't head into the ghosts' path. Due to the new layout, these corners are slightly altered, with the cyan ghost choosing to circle on the bottom of whichever side the player is on. Otherwise, the AI seems to be implemented exactly the same for the new layout.
The new layout has a couple of traps that the player has to contend with. Ghosts travel very slowly by the side warp gates, but, as stated, those are now much harder to reach in the new layout. There are much longer straight-aways in this layout, giving the ghosts more time and area to corner Pac-Man and trap him (so long as he can't slip right by them via that same bug). Pac-Man is always able to travel faster around corners than the ghosts, so the general lack of slinky corners make things more challenging.
Otherwise, the layout is roomier, which should give the player a bit more of an advantage. The extra power pellet certainly helps as well, making the game interestingly balanced. Reports say that this version of the game has 255 levels plus one kill screen, just like the original, so hopefully Google Pac-Man will be hosted somewhere outside these 24 hours to give someone a chance to reach it and show us what it looks like.
Google Pac-Man, as Google's first interactive header, is an incredibly interesting experiment, showing us all for perhaps the first time what the original Pac-Man programming can do on new layouts. Google's been rewarded with even more news coverage and traffic than usual today, so hopefully it's something we'll see more of in the future. Until then, I've got about a million more dots to eat.