To be fair, it's four zones with three acts each, which works out to the same number of levels as Sonic 3 (six acts of two zones). But to also be fair, Sonic 3's levels were much bigger and more interesting and varied (and having more zones with fewer acts was a big part of that).
My main complaint with the game (apart from the horrendous physics and lackluster music) is that the zones are complete rehashes. There is nothing new in terms of settings. Casino Streets Zone looks exactly like a 2.5D Casino Night Zone. Mad Gear Zone looks exactly like a 2.5D version of Metropolis Zone. The final boss is the final boss from Sonic 2 (that's the pre-Super final boss; I haven't been buggered to get the seventh Emerald yet and don't know what that boss is). I don't think there's a single new badnik in the entire game. In Sonic Advance, the zones for the most part fit into the classic Sonic archetypes, but they all put a new spin on them or combined them or something.
Sonic Advance is Sonic 4 (other than not being able to play as Super Sonic in the levels). This thing is an example of what not to do when making dumbed-down 21st century reboots (like Star Trek 09 or New Super Mario Bros; both examples of how to do it right).
Wait and see if Episode 2 fixes the Spin Dash, does something original, and is under 1000 points (and has Tails and Knuckles (That's another thing -- Sonic Advance continued the tradition of adding a new character with a unique playstyle with each iteration, and did a better job of it than most people give it credit for)).
(I know I'm going on about Sonic Advance a lot, but it just completely baffles me how Dimps could get it so right back then and so wrong now. Why is it that the only time they can't make a game worthy of being called Sonic 4 is when that's what it's called? Stage fright?)