A round-up of fun Linux diversions.

When people talk about computer gaming these days, they invariably mean commercial games running on a Windows platform. Few people realize that Linux can be more than just a very good Web or file server. Even fewer people are aware of the many open-source or otherwise freely available games available for Linux.

I'm not really a serious gamer, but I do occasionally enjoy a good diversion. Over the years, I've encountered some very good games and about as many duds. Some of the games I highlight in this article require OpenGL in order to run. Others have multiplayer capability. A few will run on a quite modest Linux workstation. All of them are fun and worth installing and playing.

AstroMenace

I initially downloaded AstroMenace because I was looking for a Galaga clone for my wife and oldest son. I didn't end up with what I was looking for, but I think I did even better. In AstroMenace, you pilot a ship that is constrained to the lower portion of the screen while enemy ships, asteroids and weapons attack from above. Your goal is to protect your ship while destroying as many enemy ships as you can with various weapons.

Figure 1. AstroMenace

After each mission, players are given the opportunity to repair and upgrade their ship using currency earned by completing the mission. Weapons and propulsion upgrades are available, as well as improved guidance and power generation systems. The ship's hull has multiple weapon mounts and can accept a variety of different weapons in various configurations. For example, you could put particle weapons in the front two positions and missiles in the rear mounts, and during the battle, you could fire the two banks of weapons independently. Eventually, you can build up a ship with considerable firepower.

Once your ship's upgrades and repairs are complete, you are presented with a mission briefing, and the next mission begins. The enemy ships approach in formation, and at first, it seems like they should be easy to defeat, but they just keep coming...and shooting. Completing the mission becomes a challenge.

The graphics in AstroMenace are absolutely stunning. In addition to lots of rich colors, AstroMenace features multilayered graphics that give the screen the illusion of depth. As the enemy ships move in from the top of the screen, you also can see stationary nebulae and chunks of space debris moving at various speeds. The screen appears to be a portal looking out over the depth of space during a battle. It's a very unique visual effect.

The sound also is very well done. The music tends to be more like military anthems, but the ship noises and explosions sound really good on a decent set of speakers. Turning the volume up past a certain point allows you quickly to forget that exploding ships don't make any sound in space.

Deadly Rooms of Death

Who wouldn't be intrigued by a game called Deadly Rooms of Death? Deadly Rooms of Death, or DroD, is a puzzle game where you have to navigate through a maze, avoid various hazards and solve a puzzle, all at the same time. Despite its name, this game is more of a thinking game than an action game.

Figure 2. Deadly Rooms of Death

In DroD, you are in a maze, as seen from above, that spans multiple screens and levels. Each level is inhabited by various creatures, such as cockroaches, giant worms and blobs, which you either have to avoid or kill with your sword. The creatures move in predictable patterns, and rather than adding an element of chance to the game, the creatures become part of the puzzle you have to solve to progress to the next level. You have to kill all of the creatures to progress to the next level, and some creatures may be behind closed or one-way doors, which you have to figure out how to get past.

I installed DroD on my laptop and played it for hours a few years ago. It's a great game to play when you have only a few minutes here and there, like at the airport or right before a staff meeting. The game's graphics are bright, colorful and well animated. The puzzles range from trivial to very complex. If you are prone to frustration, this isn't the game for you. Otherwise, DroD can be fun to play for hours without becoming repetitive.

War Zone 2100

War Zone 2100 is set in a post-apocalyptic world on a 3-D topographical map that you can scroll around with your mouse (Figure 3). You are in command of various military units, such as trucks, tanks and gun towers. The game is broken down into individual missions that are outlined to you before the game starts. Mission objectives range from establishing a viable base of operations to finding and destroying enemy encampments.

Figure 3. War Zone 2100

The first mission objective is simply to establish a home base with a power plant, a research center and a few factories. Of course, all the structures are nicely animated. Then, you must find and destroy a few enemy installations. The trucks do all of the construction, once you tell them what to build. After you build a power plant, you can have the trucks build a factory. Factories are where you get more trucks and tanks. Building a research center enables your troops to research new technology, such as better weapons and new types of tactical units and structures. Pretty soon, you're able to build automated gun towers. Sweet!

Once you've built up a small army of tanks, it's time to go looking for trouble. Trouble comes in the form of scavengers who have built up fortresses complete with fences and gun towers. Inside such a fortress, you'll find barracks and various other structures. You may even encounter a fortress perched on the top of a hill. However, long before you find the enemy's fortresses, you'll probably encounter one of its patrols.

The scavenger's patrols are composed of individual infantry men on foot and in vehicles ranging from three-wheeled all-terrain vehicles to small missile launchers. Scavengers practice gorilla warfare tactics and constantly sneak up on your units, attack and quickly retreat. Finding and routing the enemies while managing your ever-growing resources is quite a challenge.

The battles feature realistic sounds and animation. You can watch the gun turrets turn to aim at a target. The infantry men will crouch down when they fire their weapons. Smoke bellows from damaged tanks. While you watch the action, you hear the sound of heavy caliber machine guns and explosions. You can hear the tanks squeaking into position. You even can hear the occasional bullet ricochet. For all its sophistication, War Zone 2100 is a game I almost passed up, until I witnessed my first battle scene—then I was hooked.

The Battle for Wesnoth

The Battle for Wesnoth is a turn-based fantasy strategy game where you build up an army and go on adventures, such as regaining the throne of Wesnoth or defeating a horde of undead warriors. The game is played on a hexagonal map with various terrain types. Once you've selected a scenario to play, start the game by recruiting new units into your army or recalling units from previously played scenarios. Then, as with most games of this type, you tell your units where to go and whom to attack.

Figure 4. The Battle for Wesnoth

This game features different types of units, Bowmen, Elvish Fighters, Horsemen or even Skeleton Archers. In addition to individual names, the units have various abilities, traits and weapons. As the units win battles, they gain experience points and eventually progress to higher levels and correspondingly higher ability levels. The fact that you can recall units from previous campaigns opens up the possibility of creating a band of very powerful units for use in future games.

The Battle for Wesnoth comes with six different single-player campaigns with many more user-contributed and multiplayer campaigns to play. Each campaign starts with a brief story describing the setting and goal of the campaign. Players might be told that to win, they must slay the Black Mage, but that they will lose if their leader is killed. The game starts with strategic positioning but quickly becomes a multifront war. Completing the campaign, advancing units to higher levels, withdrawing wounded units and battling enemy units, combined with compelling story lines, makes The Battle of Wesnoth a game that you can become immersed in for hours.

Torcs

Torcs has to be the best open-source driving simulation and certainly rivals commercial offerings as well. Torcs also has the unique distinction of allowing players to build their own cars to race or race against. I'm not talking about selecting a body and color from a list and then upgrading it like you see in many racing games. I'm talking about using a program like Blender to create a new body style and a C++ API to control the vehicle. The result is any body style you care to create and as much racing prowess as you can give it.

Figure 5. Torcs

Although describing the process of developing a new car for use in Torcs might warrant an article of its own, describing the racing experience in Torcs is simple; it's everything you could ask for in a racing game. The graphics on some of the tracks are pretty realistic. Some of the cars are absolutely sexy, ranging anywhere from a Baja Bug to an AC Cobra. Each car is well modeled, both in appearance and in behavior. I expect different handling characteristics from a NASCAR than I would from a Formula One, or a car that happens to be airborne. The cars even behave differently depending on the track and the type of surface on which they're racing.

The main thing that makes Torcs such a big winner is the game's attention to detail. The cars' brake lights work. The cars have different acceleration curves and even get witchy when they come to the top of a hill and gain a little altitude. When viewed from the side, the cars' brake disks glow red when the brakes are applied heavily. Even the engine sounds are appropriate for the type of cars in a race. The normally aspirated V-8s sound different from the turbocharged 4s. Skid marks on the track are standard fare, but dust kicked up from the car in front of you is a nice touch.

Torcs includes various tracks. You can race on a NASCAR oval, a dirt track or one of many road races. Some of the road races can be exceedingly challenging, forcing the racer to navigate long straightaways that turn into tight hairpins.

Though Torcs does support a split-screen two-player mode, a game of this quality really begs to be network-enabled. Even so, Torcs is both realistic and addictive.

BZFlag I remember playing BattleZone in the arcades, so I thought I had an idea about what BZFlag was all about. Wow, was that setting the bar pretty low. Forget about vector-based 3-D graphics. How about OpenGL, fully textured graphics? Where BattleZone had fairly brain-dead opponents, BZFlag has fairly aggressive robotic opponents as well as real, live opponents from across the Internet. Figure 6. BZFlag For those of you who are young enough never to have played BattleZone, BZFlag is a 3-D tank battle game where you have to navigate around various obstacles and shoot opponents with your cannon. The challenge comes from the fact that everyone in the game has a radar screen, showing the location of all the other tanks. So the game is more than simply sneaking up on your opponents and blasting them; you have to out-maneuver and out shoot them. Depending on how the BZFlag server is configured, the game may have flags that you can pick up to gain additional weapons, shields and so on. Some flags are beneficial. Others are harmful, and you don't know which are which until you pick up the flag. Some servers are configured to allow the tanks to jump to avoid incoming artillery fire. Presumably, the tanks are equipped with some sort of rocket engine. BZFlag can be played in either of two modes: Death Match, or Capture the Flag. Thanks to BZFlag and my seven-year-old son, this article almost didn't get written on time; the game is a lot of fun and appropriate for gamers of all ages.