It's easy to like Astro Tripper, the latest frenetic shoot-'em-up from the makers of Live Arcade's Mutant Storm series. It's just difficult to get too excited about it. It's a solid and enjoyable PSN arcade experience but it never quite finds the hook, or achieves the sublime crescendo, that defines the best of its genre.
For reasons left wonderfully unexplained, your lone spaceship must zip to and fro across fourteen horizontally-scrolling stages. The goal is simple: clear out all the enemies and you move to the next level. The circle button flips your craft over so you can fly swiftly in the other direction, or you can fly backwards if you want to fend off encroaching aliens as you retreat. On the harder difficulty levels, you can even fall over the side of the level, putting even more pressure on your nimble navigation skills.
You have two attack options, swapped with the square button. The blue laser attack offers focused power directly in front of you, while the red sweeping attack will hit broad swathes of enemies above and below your position, but does less damage. Periodically, power-ups appear and boost the size, strength and range of whichever weapon is selected. Scoring, meanwhile, uses a simple cumulative multiplier that ranks up and offers bonus points for consistent destruction, but starts to decrease should you allow your onslaught to slow down. There's a time limit for each stage as well, just to keep you moving.
It's a remake-cum-sequel to PomPom's 2001 shareware hit Space Tripper, but its DNA goes back further than that. Retroheads will have no trouble in spotting the similarities to the masterful Uridium, which also tasked you with speeding left and right over small levels, dodging and zapping bad guys against the clock.
There's wisdom in riffing on an under-exposed classic rather than offering up yet another twin-stick blaster but the downside is that, aside from the obvious graphical improvements, Astro Tripper doesn't really have anything particularly interesting to add to Andrew Braybrook's 1986 template. Having established its back-and-forth two-weapon framework, it never hits a groove where those choices become more than affectations. You're restricted to firing only left or right, using only two weapons, but there's no compelling gameplay reason why that's the case, no moment where you realise that this is the only way the game's ambitions could be realised.
Of course, this is a rather high-falutin' criticism to level at a cheap downloadable arcade game, and for the price - a very reasonable GBP 3.19 - maybe being "good" is all that's required. It's certainly a moreish little treat, which builds up an absorbing rhythm as you advance through the stages. Enemies are varied, and the fact that smaller foes can evolve into more deadly, but also more valuable, forms over time adds a dash of strategy to the proceedings. Do you hammer through the basic enemies quickly to build up your multiplier, or wait for them to change so you can score ten times as many points for their destruction?
It's a tough game, however, and not always in a good way. A certain ferocity is required for any shoot-'em-up, but Astro Tripper sometimes feels haphazard in its design. In a game where even the easiest of the three difficulty levels can be a real head-banger, and where checkpoints only activate when you clear each quarter of the game, a little leniency goes a long way. The boss fights initially require too much trial and error - though PomPom is apparently going to fix this - while the inertia-heavy controls make it too easy to glide into a spawning enemy, losing one of your three lives in the process. With no way of winning more lives, thus hastening the Gamer Over screen, any punishment that feels even slightly unfair leads to frustration rather than exhilaration.
Extra longevity comes in the form of Challenge Mode, which offers a series of unlockable mini-games, where play is tweaked to accommodate various victory conditions. These are often more entertaining than the core game, and you may find yourself wishing that these elements had been incorporated into the whole rather than served up as a side dish. There's no multiplayer - despite the "Single Player" option on the menu implying otherwise - but online leaderboards and Trophies add to the competitive edge. It's standard fare though, as the scoreboards aren't as cleverly integrated into the game as they are in, say, Geometry Wars 2, while the Trophies have been blighted by annoying sync issues.
It's wonderful that the classic shoot-'em-up genre is making a comeback (some fans will claim that, like heavy metal, it never really went away) but this also means it's no longer enough to coast on the nostalgic thrill of button-blasting gameplay. Simplicity of concept requires a certain depth of gameplay to truly take flight, and Astro Tripper doesn't quite get there. It's a fun and affordable distraction, certainly, but with games like Super Stardust setting a higher benchmark for PSN shooters, that's not quite enough to earn a place on the 2009 high-score table.