Like the Wild ARMs series and Legend of Zelda series, Golden Sun tends to have a lot of puzzles, particularly in the game's numerous dungeons. Whereas the Wild ARMs series has character specific tools, Golden Sun lets the player use various Psynergy spells in the characters' repertoires to solve these puzzles. A typical puzzle may involve moving out-of-reach statues using the Move Psynergy, or creating frozen pillars out of water to use as platforms with the Frost Psynergy. There are lots of different spells that can be used in the field for these puzzles, and most puzzles involve combining one or more of these Psynergy spells with more traditional "move the blocks around" puzzle elements. All together, I think it works rather well. Unfortunately, there are a few annoying aspects of the system that come up time and again to make the experience unnecessarily frustrating.
The first problem with Golden Sun's puzzle system is that Psynergy spells cost the same amount of Psynergy points to use in the field as they do in battle. So, using the Frost spell to create a frozen platform costs Mia five PP. While this is not a whole lot of Psynergy points in the greater scheme of things, it still can add up, particularly in the early parts of the game. This problem is further compounded by the fact that the character still has to pay the cost of the spell if the player miss-aims it, which can happen quite frequently.
This comes up the most when using Ivan's Mind Read and Reveal spells to explore towns. Even though both spells only cost one PP apiece, I typically use Mind Read on every NPC in a town to find valuable information and Reveal to sweep every square inch of the town for hidden treasure. It can quickly add up to be 40 or 50 Psynergy Points. In one early town (well before Reveal is even added to the equation), Ivan ran out of Psynergy points before I had finished such a sweep. Since Psynergy points do not recover naturally inside of towns, I was forced to stay at an inn in order to even finish my exploration of the town, and then stay at the inn a second time so that I could have full PP before setting out.
The other annoying drawback of the Golden Sun system has to do with the availability of the necessary Psynergy for puzzles. While some of the most common puzzle Psynergy (namely Move, Read Mind, and Reveal) are always available as part of one or more character's spell lists, the availability of the rest of the necessary spells is sometimes in question. For example, many spells, such as Catch, Force, and Cloak, are only available to a character equipped with a specific item. Other spells, including Whirlwind, Growth, and Ply, are learned naturally by various party members, but are only available to characters with specific class set-ups. For example, Whirlwind is only available to Ivan if he has only Jupiter Djinn equipped. Therefore, the player is often required to temporarily rebuild his Djinn list in order to make required Psynergy spells appear, which often turns puzzle solving into more of a hassle than a fun diversion. The numerous and sometimes redundant equipable items also eat up a lot of the very limited inventory space of the four characters.
My complaints about the interactions between Psynergy and puzzles could be solved by two quick changes. First off, Psynergy spells should not cost PP when used in the field. While this change would not have an appreciable effect on game balance and combat, it would alleviate the frustration from running out of PP in the middle of a town. Second off, the Psynergy spells that can be used in the field for puzzles should be made a permanent part of the character's Psynergy lists. For example, instead of giving the player an equipable item that bestows the Force spell, just have the same event add that spell to an appropriate character's spell list. This way, the player won't have to dig through menus to re-equip Psynergy all of the time.