Studio Evil has released Syder Arcade (http://macte.ch/SasoI), an US$7.99 game for Mac OS X. A demo is available for download.
Here’s how the game is described: “Arcade is a multi directional side scrolling shoot’em up that nods to old-school classics like Defender or the Uridium games. The gamer will play the part of one of the humans from the space colony of Miza, attacked by a mysterious alien force. Syder Arcade will challenge you to six levels of pure arcade action.”