Sonic the Hedgehog CD was well-reviewed, but sales were limited by the requirement to buy the Sega CD/Mega-CD add-on for the Sega Genesis/Mega Drive. The game was ported to Windows in 1996 as the first of many games under the Sega PC brand. Sonic CD introduces a time travel element to the gameplay. Speed posts labeled "Past" and "Future" are scattered throughout the levels. After activating one, Sonic must run at top speed for a few to travel to that time period. A robot-building machine is hidden in the past in each level which, if destroyed, there are no longer robots in the future. If the machine is not destroyed, the future is full of robots and pollution. Each level is broken into three zones, with the third zone being a boss fight with Dr. Robotnik in the future. Sonic CD will not work in any NT-based operating system, even in Compatibility Mode, unless patched with a fan-made patch called SonicCDFix.
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