The concept of time travel is certainly appealing: who wouldn't jump at the chance to rectify personal regrets or prevent history's most brutal wars? In video games, this contrivance usually serves up a juicy excuse to whip up imaginative weapons, historic foes, and memorable arenas, but somebody forgot to tell Time Ace.
It's fitting that the first level sends you after an evil time traveler's locomotive, given that most of the game rides on rails. Though you might occasionally get to circle back on generators or buzz bosses, finding your route just means following the top screen's gyrating arrow. Trying to deviate from this preset course tends to result in being forcibly steered to an explosive death, but once you accept that you're riding a glorified rollercoaster you'll find that your only real frustrations relate to some mercifully uncommon instances of poor collision detection.
The resulting experience is remarkably simple and ridiculously short; cruise through nineteen epoch-hopping levels where you only ever need to decide what to shoot at next. Unfortunately, no matter how many floating power-ups you grab, the only remotely interesting weapon you'll ever acquire is a gun that fires green circles, and the endless waves of dull, slow-moving craft do nothing more than spray a handful of bullets and wait to be executed. The tedium is broken up by larger quarry like galleons, tankers, and a handful of repeating bosses, and a few of the later levels demand some tense flying through narrow spaces, but even then the core action remains a tepid shooting gallery. Only the Atlantis bonus level adds any offbeat mechanics to sink your teeth into.