Battles are turn-based and menu-driven, but like everything else, come with a twist of modernization. During their turn, characters can perform a normal attack, use special attacks, guard or attempt to flee. Choosing to attack deals a little damage, but if you manage to score a critical hit, you'll earn the opportunity to punctuate it with an additional critical hit by timing your button-press with an on-screen "X".
Again, if you're hoping to do any significant damage to enemies, you'll have to use special skills. These, of course, drain lots of mana but are incredibly useful for getting you through your first few levels. You can also purchase mana-restoring items in towns. Early on, you have to really manage your finances, but like any RPG, you'll eventually get to the point where you have enough money to buy and sell entire stores.
Characters can team-up for attacks provided their turns are back-to-back, though like every other skill, you'll need to purchase them before you can use them. Crimson Gem Saga uses a skill unlock system similar to Diablo, but everything is hidden behind question marks. To reveal skills, you first need to dump Skill Points (SP, which are earned in battle alongside experience) into the locked skill block. The advantage to the system is that you can skip around the skill tree and only purchase certain skills, but when everyone in your party shares the same meager pool of SP, it is a hassle and a waste. I can see where the developers were trying to go with the system -- as you progress through the game, the hassle and frustration ease. But it also places unnecessary strain on what is already a tough opening act. The system would have had just as much impact if characters had their own SP pool rather than having to share.
Difficulty is the only major issue facing Crimson Gem Saga, and it is a somewhat subjective one at that. One player's challenge could be another's cakewalk. The one thing for certain is that Crimson Gem Saga is a strong entry into the PSP's line-up of RPGs. Players with more "modern tastes" may find it's old school sensibilities ancient for their tastes, but anyone in the market for a simple, fun RPG like you used to play on your SNES will want to pick up Crimson Gem Saga.