The expression Twitch factor is most commonly associated with arcade games. It describes the level of action that a game provides: the more frenetic the game, the greater its twitch factor. In this month's installment of The Game Room, we'll be discussing two new titles that unquestionably have heart-poundingly high twitch factors -- Deimos Rising, from Ambrosia Software, and Spider-Man, from Aspyr Media.

Rising Star

David Wareing has once again joined forces with Ambrosia Software to create a twitch masterpiece: Deimos Rising, the long-awaited sequel to Mars Rising. Inspired by classic coin-op arcade games of the 1980s, Deimos Rising is a futuristic shooter that puts you in the cockpit of an assault fighter as you fight to quell a rebellion that has broken out on the terraformed Martian moon Deimos. That's all the pretext you'll need, because when you're playing Deimos Rising, it's all about the action.

This title harks back to the days when arcade games cost a quarter. Waves of enemy ships assault you from the air while ground installations such as cannons and tanks fire at you. Successfully vaporizing your enemies generates goodies, which you collect for point bonuses, shield power-ups, bonus multipliers, and more.

Because Mars Rising is a Mac-game classic, Deimos Rising had big shoes to fill. This game is more difficult than its predecessor, as it was developed to appeal to Mars Rising veterans. Its challenging learning curve can even lead to frustration: ground targets are tougher to take out, and enemy aircraft are more aggressive.

Deimos Rising has better graphics than Mars Rising, and the action is as smooth as silk. Each new level equips your craft with new arrays of offensive and defensive hardware to help keep the wolves at bay.

You can play new games at the start of whatever level you last completed, but there's a catch: you'll start that level with only a single ship. To start with a full set of ships, you have to play from the beginning. Such a limitation seems unnecessary outside of an arcade, but the challenge helps make the game last longer. Perhaps some folks will feel they get more for their money that way.

The game's two-player mode lets you and a friend blast away at Deimos's rebels from the controls of one Mac. You and your wingperson can use either different areas of the keyboard or different game controllers. Mac OS X doesn't support game pads natively, though you can get one to work with a third-party utility such as CarvWare's GamePad Companion (http://www.carvware.com).

Deimos Rising is a worthy successor to Mars Rising, and it's everything we've come to expect in a game authored by David Wareing. With better graphics and sound and the same smooth game play, it'll definitely appeal to fans of classic arcade games. And it should grab some new recruits, too. Download it and try it out for yourself.

Does Whatever a Spider Can

At long last, we have a spider-sense-tingling action adventure for the Mac. Westlake Interactive and Aspyr have brought the new Spider-Man title to the Mac, courtesy of Activision. In this game, you take on the role of Peter Parker, student-turned-superhero (thanks to a radioactive spider bite).

The upcoming opening of Spider-Man the motion picture will undoubtedly bring a continued interest in this title, but Aspyr's game is more influenced by the comic book than by the movie. Comic-book-style covers mark new levels, and narration from Spider-Man cocreator Stan Lee peppers the game.

The plot: Spider-Man has been framed by his archenemy, Dr. Octopus. The cops, Spider-Man's other enemies, and thugs galore swarm the city, and Spider-Man has to save the day and clear his name before it's too late.

No Spider-Man epic would be complete without confrontations involving costumed supervillains. And this game doesn't skimp -- Spidey will take on enemies such as Scorpion, Venom, and Rhino. He'll also hook up (briefly) with his friends Black Cat, Daredevil, and The Human Torch.

Spider-Man is a twitch-laden, 3-D-action game rendered in a third-person perspective. You control Spider-Man from just over his shoulder, and in this way the game is evocative of Tomb Raider and Oni. Spider-Man can climb walls and ceilings, rappel using his special web formula, spray sticky webs on his foes, and apply some martial-arts-style kicking and punching to take down his many enemies. Like most third-person games, there's a lot of puzzle work: you must trigger a button to open a lock, for example, or find a safe place to store a bomb before it explodes.

This game's roots are in the video-game-console world, and it shows. Spider-Man is ideally suited for use with a game pad or some kind of game controller. Spider-Man works adequately with the keyboard, but the default key map is cramped and awkward (it can be customized, however). Because of system limitations in Mac OS X, there was no support for game pads at the time of this writing (although Spider-Man may work with GamePad Companion).

You can save your game between levels, so don't worry about having to beat this title in a single sitting. Don't look for multiplayer capabilities, though -- Spider-Man's single-player limit is another manifestation of its video-game-console roots. But it has some nice amenities -- a training mode helps you hone your skills (and there's a Kid mode that provides a less frustrating approach for younger gamers). You can check out custom Spidey costumes and enter cheat codes if you get too frustrated (they're available at various Web sites). You can also adjust graphics resolution, sound effects, and keyboard and game-controller layouts. A Gallery area lets you watch movies and check out images and biographies of the game's characters.

Spider-Man's graphics are simple and a bit on the blocky side. Characters don't lip-synch dialogue (their mouths stay still), and interstitial movies are indistinct. These are all understandable and unfortunate problems, given the title's pedigree as a Sony PlayStation game.

Camera control is my single biggest complaint. Automatically controlled, the game's camera is usually positioned behind and above Spider-Man, but in certain locations, the camera swivels around to awkward positions. This occasionally caused action to pause at inopportune times as I waited for the camera to reorient itself, allowing the bad guys to get in a few licks before Spidey could take them down. I would have preferred a customizable way of tracking Spider-Man's moves or the ability to switch quickly between fixed camera positions.

Spider-Man is a fantastically fun and challenging title. Like many Mac game titles brought over from the console world, it has a few warts, but none serious enough to keep you from buying it. If you're looking for some web-slinging superhero fun, grab this game.

Macworld's Buying Advice

Deimos Rising offers some classic, albeit occasionally frustrating, Mac arcade-game action. Spider-Man may have a few flaws because of its video-game-console heritage, but it's still superfun for lovers of this comic-book superhero.