13-3 is decent but nothing great or spectacular. For most of the game it's simply Lightning against the world. She's not a particularly well designed character and she's not particularly likable so having the entire game revolve around her is a questionable decision.
Despite only one playable chartacter, the battle system is decent but there is no leveling up in the traditional sense. Instead you gain stats based on quests completed. Abilities are "drops" from enemies and you can enhance those abilities by farming them and combining them to make them stronger. This includes basic abilities like "attack." However, the job system is pretty decent and it's fun to play "dress up" with Lightning.
Keep in mind if you are a completionist, you will NOT be able to get Platinum or 100% on a single playthrough. There is a fairly robust NG+ system in place though which brings me to my next point...
This game features a clock. When the clock runs out, the game is over. This is one of the most controversial features of the game and most view it very negatively. With that being said, there are ways to abuse the clock system and freeze the clock for short periods of time. And once you understand the game and where to farm things, you can keep the clock froze almost indefinitely. One big problem though is the amount of stuff that must be done at certain times of the day which can make the first play extremely difficult without a guide. Without a guide, you're likely going to run out of time and be forced to start from the beginning. But remember how I said there is a robust NG+ system? Starting over doesn't mean starting over at level 1 (though there are no levels). You start the plot over but keep pretty everything except key items.
Anyway, that's a lot more than I planned to write. In the end it's an OK game but not a great game.
