Hands on with Kryzer Prologue on iPhone

There was a point in the early days of the arcades when, all of a sudden, gamers tired of the vertical shooter. Space Invaders had nailed the concept to history’s walls, but after a while its clones weren’t enough to keep the Japanese coin shortage going.

And so game developers began to get quite imaginative about different ways for players to shoot down enemy ships. With the App Store being as new as it is, all the old concepts could be brought out and paraded once again, but already we’re looking for variations. It’s to this call that Kryzer Prologue answers.

It’s a 2D shoot-‘em-up in every sense - except the ‘up’ part. Rudimentary comparison would pin it as a spherical take on Space Invaders, though it's a bizarre concept that shoots higher than just putting a twist on an old game.

The play area is a circle with a pivot point in its centre. Your ship travels continuously around this pivot point in a clockwise direction, with your only movement controls being to move in and out from the centre.

A variety of enemy ships spawn at random intervals within the circle, moving in different ways. Some, for instance, simply rotate around the circle at a slightly slower pace to yourself and without moving in or out, while others cut a straight line across the diameter, or spiral from the centre to the circumference.

Your ship shoots automatically. The bullets follow the curve of the circular battlefield. Due to the relatively confined space and the various orbits of enemy ships, it takes swift reactions to avoid crashing as you line up to shoot down the adversaries and collect the extra seconds they leave behind.

Your energy level is essentially a timer, which slowly counts down to zero. 30 seconds disappears from the clock every time you crash into an enemy ship or take a direct hit as they shoot at you.

The constant stream of bullets sent directly ahead reach about a third of the way around the track until the game begins to speed up as you approach the end of a level. At this point, weaving around the increasing number of enemy ships becomes a battle of dexterity every bit as much as a high octane shoot-‘em-up shoot out.

For such typical shmup mechanics, Kryzer Prologue feels surprisingly unique. And although the in and out movement (as opposed to moving left and right) requires adjustment, it's just a part of the game’s challenge and doesn’t evoke much frustration. You may kick yourself when you move outward, instead of in, but not hard enough to leave a mark.

The clean-cut graphical style and the superb soundtrack are likely to help add a great deal to the game's appeal too. As long as the full release packs in a few surprises and tweaks to the gameplay as you battle through the levels, Kryzer Prologue could turn out to be quite a sleeper hit.