Like a weird mix between premature birth and a really frantic brainstorming session. Sonic 1 feels half baked and unfinished, it's nearly there, but not enough even as a first attempt.
It unfortunately creates a game that isn't that fun to play most of the time, even when you learn to play it "properly".
But you can feel they had something here, I think they just didn't really know what it was yet. They needed some time for their baby to grow.
Music is great tho.

(making Scrap Brain 3 just Labyrinth Zone 4 is so nefarious and sadistic it's genius, it's like the perfect in-character trap for Eggman to set)

LADIES AND GENTLEMEN THE GAME THAT WAS MEANT TO BE.
The funnest sprawliest stages, the slappiest music, the cheekiest player traps, just the best feeling. The game even handles frustration/fun incredibly well and can feel so rewarding at times.
It's a shame it takes a nosedive at around the final levels and the boss gautlent is so frustrating it almost makes you hate everything.
But I don't hate it. I replayed some stages right after a frustrating finish just to be sure, and I love it very much.

It's not perfect, it can definitely feel rough around the edges, and I think they still have stuff to improve on the Sonic formula. But it's one of those games where it's just impossible to hate it, it's just too charming and too fun.

If this had been Sonic 1, SEGA would still be in the console business tbh