Buganoids is a free arcade game with 8-bit graphics, old-school sound and gameplay, and a circular range of movement reminiscent of classic stand-up tube-shooters like Tempest and Gyruss.
Buganoids' schtick is simple and addictive: you move clockwise or counterclockwise around the "surface" of a planet, shooting into the interior to take out advancing enemy bad guys--in this case, menacing little bees, birds, turtles, and centipede-type creatures, which emerge from holes in the planet's surface. The game's interface is explicitly styled after a stand-up arcade game: under the main screen, you press photo-realistic buttons to rotate left or right, shoot straight down from where you're standing, or blow up a screen-clearing bomb. You progress across eight different planets (mostly identical in terms of gameplay), collecting different power-ups and trying to survive through each short level. In addition to your default pistol, enemies also leave behind better weapons, including a laser that shoots through multiple enemies and a homing rocket that bends toward its targets (especially useful, given that much of the challenge of Buganoids is mastering accuracy across the circular playfield). Even for such a simple game, Buganoids does a good job of integrating small, thoughtful tweaks into the game, like an icy planet that you slide on, and the ability of tricky turtles to stop and reflect your shots.
Buganoids is an excellent homage to 1980s stand-up games, and--like the best of those games--still a good bit of fun to play now, especially for old-school fans. The game is free, or you can pay to remove relatively unobtrusive banner ads.