Sonic CD would be fine if it wasn't for the way you perform the time travel mechanic. The fact that you need to keep constant speed to activate the time travel and that there are more future signs than past signs is a fucking hassle and a half. And the past signs are always in areas where you can't achive a steady pace to activate the time travel, so you wind up having to backtrack (or go more forward) to an area that allows for constant speed, and good fucking luck trying to achive that in the fucking water level.
Allow me to address this particular complaint:
Time travel in Sonic CD is TRIVIALLY easy.
How so? Well, remember this segment in Sonic 2's Hill Top Zone?
It's a pointless gag that accomplishes nothing other than amusing or annoying the player. But in CD? They're you're secret weapon for time travel.
In many levels, there exists such arrangements of springs that will always propel you back and forth fast enough to activate your time travel. All you have to do is grab a Past Sign, run into the springs, and just wait for time travel to kick in. This includes the aforementioned Tidal Tempest Zone you just complained about.
In TT1, it's right next to the Robot Generator:
...and in TT2, the Past Sign is
right next to it:
Most of the levels in the game have some kind of easy time travel trick, to the point that the ones that
don't are far fewer than the ones that do. Which, off the top of my head, only include PP2 and SS1 (And QQ1 and QQ2 in the HD Steam version, since the easy tricks don't work in that version).
If anyone cared, I could point out all the different locations of these "easy time travel" spots that I'm aware of. They're really quite handy.