Some great shooters are original, but the vast majority are variations on a theme. Mix up the same elements, give or take, and add an ingenious twist: et voila! Such is Super Crossfire HD, one of those games that's always reminding you of others, and a shooter precision-engineered around one clever idea.
The key trick here is instantaneously warping between the floor and the roof of the 2D level, a mechanic that isn't just a joy to use but is hardwired into enemy movement and how the waves work. It has basic puzzle elements - enemies will fire at the surface you're on, but it takes them a second to turn, or they have one side that's invulnerable, or they're protected by a shield - that depend on smart warping, but the trick is in being able to do simple calculations fast under fire.
Because you are constantly under fire, the black-bordered neon visuals (with an especially cool 'burnout' effect) give deadly life to pulsing energy bolts of all shapes and hues. Staying in one place for too long results in bullet hell raining down on your position, which can either be woven through or immediately warped out of. But such is the pace of Super Crossfire's shooting that most deaths come from warping out of one deadly situation and, under pressure, warping straight back in before the bombardment has passed.