Sonic CD

Sonic CD is the strangest and at the same time the most ambitious entry in the classic hedgehog series, and remains to this day the main reason to own a Mega-CD at all. Sonic chases Doctor Robotnik to the mysterious Little Planet, a small world that appears above a lake once a year and whose fate is tied to time stones. That's exactly where the game's central idea comes from: every level exists in four time layers. When Sonic builds up enough speed and runs through a sign marked past or future, he's transported to that same location's past or future, which has different graphics, different music, and differently arranged platforms.

The game therefore doesn't rely on speed alone but mainly on exploration. Your task is to find a hidden machine in the past that manufactures Robotnik's robots, destroy it, and thereby secure a good future for that zone. The levels are more intricate and much more vertical than in the Mega Drive entries, full of loops, tunnels, and hidden nooks where it pays to slow down and search thoroughly. New additions include the so-called super peel-out, a stationary run-up as an alternative to the classic spin dash, and above all Metal Sonic, who in one of the series' most famous sequences races the player at a brutal pace.

The game made use of the CD's capabilities mainly for an animated intro and ending sequence by Japanese animators, and for music played directly from the disc. There are two completely different soundtracks, Japanese and North American, and the argument over which is better still follows fans to this day; both, however, give the levels a very distinct mood, ranging from dreamy melodies to harsher, more rhythmic tones. At the time, the game felt like proof that a compact disc didn't have to mean just cutscenes but could also mean a genuinely rich action game. Today, thanks to later re-releases, Sonic CD is one of the few Mega-CD titles that's easy to access, and it's among the best-aging things the console ever released.