The biggest and most noticeable change in Puzzle Quest 2 is the graphical facelift and quest structure. Instead of roaming through connected waypoints on a vast overworld map, PQ2 takes a cue from Diablo by starting you off in a town set atop a great evil force. Predictably, you are the only one that can plumb the depths of the dungeon and eliminate the nasties. So instead of traversing roads between kingdoms from a high-level view, you are now moving room by room through a deep dungeon. Each enemy, door, and treasure chest is visible on screen, and you simply move to the next location by clicking on their associated icons. While it initially looks like this structure would afford the player more freedom as they explore, it actually ends up less compelling than the original, as it really isn
Combat fares a bit better, and implements some very unique new additions to change up the gameplay
One of the most prevalent new wrinkles in PQ2 is the addition of weapon attacks, which are gained by matching 3 or more hammer icons to gain Action Points. Once you gain enough Action Points, you can spend a turn unleashing an attack from your equipped weapon, which typically causes direct damage to your opponent. My guess is that these weapon attacks were intended to be used sparingly, but the frequency of action points available causes most matches to devolve into both players hoarding their action points, then unleashing a barrage of damaging attacks. It takes some of the intrigue out of the battles when you know your opponent can drop an avalanche of damage on you at any given moment late in combat. This becomes even more glaring when the typically brain-dead AI could finish you off in one or two very obvious attacks, but chooses instead to dink around making more matches instead of closing the deal.
You begin the game by choosing one of 4 pre-determined classes, each with their own unique attacks, spells, and abilities. While the variety of choices is nice to have, none of the classes ever feel very balanced. After trying multiple classes, I could never shake the feeling that I was either far more or far less powerful than I should have been. Some classes (like the barbarian) have very few useful skills in the early game (which makes things far harder than they should be), while their late-game skills are completely devastating (which makes things far easier than they should be). Some of the other classes fare better during the early-game, but nearly every one of them will feel incredibly overpowered once you hit the halfway mark.
One of the more positive additions is the new looting, bashing, and trap disarming mechanics. Chests found in the dungeon are plundered through a fun looting mini-game in which the player matches crowns, cups, and chests to gain cash and rare treasures. In order to bash through a barricaded door, door icons must be matched in a specific number of turns while disarming traps requires the player to match a pre-determined number of unique gems. These are all very welcome change-ups to the standard combat, and provide some unique diversions as you progress through the dungeon.