Ultimate Flash Sonic is basically someone cramming the classic Genesis Sonic experience into a browser tab. It's got all the loops, speed, and those little details—like the way Sonic's feet blur when he's sprinting—that make it feel legit.

Controls are dead simple: arrows to run, space to jump (though I kept accidentally hitting shift at first). The physics are surprisingly close to the original—you can still build momentum downhill and launch off ramps just right. And yeah, there's a password to unlock everything, which is handy if you just wanna blast through the levels without hunting for chaos emeralds.

It's not perfect—some of the level layouts feel a bit off compared to the Sega version—but for a Flash game, it nails the vibe. You’ll probably catch yourself humming Green Hill Zone after five minutes.