An RPG of high caliber... not to mention it's for the GBA. The gameplay is solid, and presents you with challenges and puzzles along your quest. The battle system is DEFINATELY one of the best I've seen, with the Djinn (think summons) that you must EARN through puzzles. It's really much more fun earning your Djinn through puzzles and non-exp. related ways (Although, sometimes, when you find the Djinn, you must fight it.), then fighting until you get to ~X~ level (which many game do with many of their summons). I like the storyline quite a bit, too. It has the perfect set up for a sequel (which it IS getting: Golden Sun 2: The Lost Age), and flows quite smoothly. I never stopped and asked myself, "Wait a sec, why am I doing this? I thought I had to...". The 'Mars, Venus, Jupiter, Mercury' and 'four elements' thing is used very well, and, although it's a bit overused in the VG world, slips in quite nicely with the Djinn and the lighthouses and stuff (Don't want to be too much of a spoiler!). Even the graphics were good. I thought the towns, caves, castles, and the world map were done very nicely. (For a GBA game, anyway...)
The only real problem I had with this game was the fact that it went to fast; especially for an RPG. I didn't get the "final boss" vibe when I finally got there, becuase just a little while ago, I was halfway through the game. Oh well... there's always GS2.
Overalll: A very good game, even if a little short. 97/100