dot.Error is a strange shooter and, sweet retro visuals aside, is unfortunately rather mediocre
The gameplay, however, gets very mixed reviews. Like most shooters, you fly around and shoot your gun at enemies. Unlike most shooters, while dot.Error side-scrolls, you need to travel both left and right to reach your enemies. The enemies you're blasting are "unmanned space rockets" which look like bricks (again, remember this is retro) and when they emerge they'll show up as blips on your map-screen. And that's about where things get dicey. Shooters are repetitive by nature - there's never much to do - and because of that for the gameplay of a shooter to be successful, you need multiple forms of enemies, different challenges, lots of powerups, and changing environments so that the repetitive actions you perform do not become monotonous and boring. The action must be pretty frenetic, while at the same time not so challenging as to make the game overly difficult. Unfotunately, dot.Error doesn't deliver here. The gameplay is repetitive, the environments are static, the enemies dull.
So despite some really great retro designs, poor gameplay prevents this one from becoming a great option for your shooting needs. Despite that, you may want to check it out just to see the design!