not a bad game by any means, especially if you just decide to play casually as sonic without getting the true ending, though the physics could be better, and the game suffers from the gba's small screen so you can barely see where you're going (i hear theres a fan project that fixes that, i regret not playing that version instead), and the game's a bit too easy and linear at times. this is the hold right to win sonic game and it shows. besides all that, its fun, the level design does at least allow you to be fast, the visuals are fantastic, i love the art style and the bosses can be pretty good.
the real problems arise if you want the true ending. i thought i just needed all the chaos emeralds, at first, but you need to get all the chaos emeralds and also beat the game with all the different characters too, then beat the game as sonic. i wish i found that out earlier, since i decided to get all the chaos emeralds right away, i looked up their locations, did a playthrough as tails, then did a real playthrough as sonic only to find out that i got the normal ending. its only a 40 minute or so game to blaze through, so doing it 2 more times wouldnt't be so bad, but the final 2 levels just go on for so long that it gets annoying. it feels like it wants to have the replayability of the classic games, but doesn't nail it. the real flaw of this game though, is the special stages. unlike sonic 1 where you had to collect 50 rings and jump in a big ring at the end of the stage, or sonic 2 when you had to collect 50 rings and jump in a checkpoint, sonic advance instead decides to take inspiration from sonic 3. in that game, you had to find warp rings scattered throughout every stage. but in sonic 3 there were several in most stages, i think at least one in every stage so you have a chance to get all the emeralds. sonic advance has jump springs. there are 7 of them, one for every emerald. elaborately hidden in various stages. one in each zone (except in ice mountain which has 2), but the act they're in is random. and if you do find them, you're treated to what might be the worst special stages in the sonic series, as you're falling in this poor 2.5d setting and have to grab rings and avoid bombs (ala sonic 2), but the hit detection just seems so inconsistent that rings will literally go right through you without grabbing them. even with save states and rewinds, the stages were damn near impossible at times. and keep in mind, simply getting all of them won't get you the super sonic ending, or let you transform into super sonic at will like the old games. unless you're willing to go through the game 4 times in a row, and the final stage a fifth time, it's just not worth it.
not a bad game by any means, but too easy and short for casual play. too bs and repetitive to complete. maybe check out that "sonic advanced revamped" though
the real problems arise if you want the true ending. i thought i just needed all the chaos emeralds, at first, but you need to get all the chaos emeralds and also beat the game with all the different characters too, then beat the game as sonic. i wish i found that out earlier, since i decided to get all the chaos emeralds right away, i looked up their locations, did a playthrough as tails, then did a real playthrough as sonic only to find out that i got the normal ending. its only a 40 minute or so game to blaze through, so doing it 2 more times wouldnt't be so bad, but the final 2 levels just go on for so long that it gets annoying. it feels like it wants to have the replayability of the classic games, but doesn't nail it. the real flaw of this game though, is the special stages. unlike sonic 1 where you had to collect 50 rings and jump in a big ring at the end of the stage, or sonic 2 when you had to collect 50 rings and jump in a checkpoint, sonic advance instead decides to take inspiration from sonic 3. in that game, you had to find warp rings scattered throughout every stage. but in sonic 3 there were several in most stages, i think at least one in every stage so you have a chance to get all the emeralds. sonic advance has jump springs. there are 7 of them, one for every emerald. elaborately hidden in various stages. one in each zone (except in ice mountain which has 2), but the act they're in is random. and if you do find them, you're treated to what might be the worst special stages in the sonic series, as you're falling in this poor 2.5d setting and have to grab rings and avoid bombs (ala sonic 2), but the hit detection just seems so inconsistent that rings will literally go right through you without grabbing them. even with save states and rewinds, the stages were damn near impossible at times. and keep in mind, simply getting all of them won't get you the super sonic ending, or let you transform into super sonic at will like the old games. unless you're willing to go through the game 4 times in a row, and the final stage a fifth time, it's just not worth it.
not a bad game by any means, but too easy and short for casual play. too bs and repetitive to complete. maybe check out that "sonic advanced revamped" though