First of all, I'll admit that I'm not much good at first-person shoot-'em-ups. However, they are very popular at the moment, with games like Quake appearing on the PC and consoles. The Revo now has its second shooter - Palmtop Software's Doom-playing ENCORE was first, and now WildPalm have written Terra Force.

The storyline is so simple as to be nonexistant. You are in charge of a tank (three models with different strengths are available, but two of these tanks must be earned) and you have to shoot the other tanks. All the action takes place in a large arena, meaning that you don't get different levels or any particular final objective. Terra Force does track your high score, though, so you could try to beat that.

Controlling your tank is easy - you just use the arrow keys to move around and Ctrl to fire. You can die from a single shot, which all enemies will die from as well, so you'll need the three lives that you get. Infuriatingly, it's sometimes impossible to hit a tank from a distance because you can't aim accurately enough. Surprisingly, the range of your missiles is never a problem, as they seem to be able to travel the entire length or breadth of the arena, although they are relatively slow. You can take advantage of their slowness by hiding behind something in the 3D arena, or just moving out of the way, before they hit.

It's difficult to know where you are in the arena because it is largely featureless. I noticed one or two marks on walls, but that's it. It creates a feeling of being lost in the labyrinth, which works quite well, although it can be difficult to find your next randomly-placed enemy. You can keep playing forever, theoretically, as new enemy tanks are created when you destroy others. Their Artificial Intelligence varies, but it's normally pretty good. Some enemy tanks make a hobby out of shooting walls pointlessly, though, but this makes them easier to find because you can hear the shots.

The graphics in Terra Force are very good for a Psion game, looking somewhat like the PC game Doom, although your battery will probably be drained faster than if using most other Revo programs, such as Word, because it uses the full 16 greys the Revo can display. Most programs just use 4 of them. Terra Force's sound isn't bad either, as it gets louder and quieter as you move nearer and further away from the source.

I do have a few complaints with Terra Force, though. The caption on the Terra Force Extras bar icon is severely clipped on the Revo. Normally I don't mind parts of letters being missed off, but 'Terra Force' appears as 'erra Forc' which sounds like problematic cutlery! The Sound menu option toggles between 'Turn Sound On' and 'Turn Sound Off', which isn't normal for a Revo program - there ought to be either be a tick or no tick next to the menu option like, for instance, the 'Show toolbar' option in Word.

The Ctrl key is used to fire, creating another problem. There are no keyboard shortcuts for menu items (Ctrl is used to activate them, normally), which also means that you cannot close programs with the standard Ctrl+E shortcut. This means that you must normally go to the menu to close Terra Force.

Finally, Terra Force is another victim of a clunky help system. Most Revo programs use the built-in Help program based on Data, but Terra Force uses its own proprietary system which involves choosing a topic from a drop-down box. The topic text appears in a box which only shows three and a half lines of text, but never gets a scrollbar, even when it needs one. You must tap in the box and use the Up and Down arrow keys to see hidden text.

Overall, Terra Force is a good first-person shoot-'em-up which will appeal to those who like Doom and Quake-type games. It's simpler, but easier to pick up because of that. Terra Force does have a few annoying problems, but these shouldn't interfere with standard gameplay.