Sonic CD builds on Sonic 1's foundation, but is an overall more comfortable adventure I feel. You're able to tailor it more to the kinda Sonic experience you want out of it. You can do the more classic approach of doing the special stages and getting all the Time Stomes or you can make the effort to travel through time, explore all the levels and destroy the machines in the past. It's up to you! Granted, the level design is made moreso for the ladder playstyle, with big vertical levels that you speed through fairly quickly if you're just heading for the goal. Plus when you do go for the machines in the past they can sometimes be in pretty bullshit positions. Either way I don't think this game is quite as amazing and well-structured and designed as 2 and 3, but still a lot more enjoyable than the original. Plus the japanese soundtrack rules.