Paper Mario: Sticker Star is a confused game. It doesn't quite know what type of Mario game it wants to be and this often leads to its undoing.
The classic Paper Mario games offered deep, RPG stylings and a great sense of humour. Sticker Star retains neither of these things. In an effort to streamline the game for 3DS, Nintendo have stripped away a lot of what made the older offerings so much fun. The badge mechanic (which was essentially armour equips and stat buffs) have been entirely thrown out and the only real bonus you can gain is by finding HP+ Hearts which are scattered accoss the world and offer meagre health bonuses. Exploration and the world in general is also more streamlined and now plays more in line with a traditional 2D Mario game, selecting a level from the overworld akin to Super Mario World. Some fun is had with exploration, including levels that are hidden away, but offer nothing beyond that.
More changes can also be found in the combat too, which has undergone a transformation of sorts. Combat still plays out like the older games but is now reliant on stickers. Stickers are one time use attacks and essentially your moveset. This ranges from standard jump and hammer attacks to something more adventurous such as Red Shells and Fireballs or even special attacks. Special attacks are unlocked by finding special 3D items in the world such as Trumpets, Baseball Bats or even Lucky Cats. Battles with tougher enemies can be really exciting and often turn into tense, tactical affairs especially as your stickers dwindle down during the course of the fight. Stickers can be bought from shops, or found scattered across the world and will need to be peeled off walls and smashed out of ? Blocks.
Initially, it can be quite fun finding new stickers, seeing how they affect different enemies or what bonuses they offer in combat (attaching a Spike Helmet will hurt enemies that attack you, for example). Stickers can also come in different forms, and depending on their form can be more powerful or offer different effects, this extends to shiny stickers which will be more powerful than the base form, or worn-out stickers that are not as powerful. There are problems with the sticker mechanic, however. Peeling them off of everything becomes tedious after a few hours and combat offers little to no reward beyond coins and expunged stickers. The page limits on how many stickers you can carry at one time are also frustrating in the earlier parts of the game, especially when you have rare stickers like Scissors, which take up four sticker slots. Unfortunately this means that fighting enemies is something that is best avoided unless you absolutely have to.
Stickers can also be used in puzzles, fixing missing bridges and gates that have been removed by Bowser's minions by using the "Paperise" mechanic, wherein Mario will rise above the game world and place stickers on things or remove incorrectly placed doors or switches. There are also other environmental puzzles that require you to place stickers over things (in one instance you have to cover two fans to stop them from pushing you off a bridge) but these can further induce frustration as larger puzzles tend to need special stickers. If those stickers have been used in combat then you'll have to backtrack either to the store or the corresponding world you found that special sticker in, something which just feels like an artificial extension merely dragging the game out longer than it needed to be.
At least the game still holds its sense of style. Paper Mario's presentation is as gorgeous as ever, 3D adds a nice sense of depth and scenes often look like dioramas. There are a handful of new enemy types which are creative too, such as 2-ply Goombas or Paper Cone Goombas (which take advantage of the 3D) or Shiny equivalents (which are more powerful versions of the standard enemy type) they're what you would expect from a Mario game at this point, Shy-Guys, Hammer Bros., Koopa Troopers, but they all look great in the Paper Mario world.
It is such a shame that Paper Mario: Sticker Star doesn't know what it wants to be. It tries to blend some of the best elements of other Mario games and often feels confused because of it. The sticker system is bogged down by the tedium of having to collect them which in turn is followed by the frustration of using them on lesser enemies, combat is best avoided and offers nothing substantial and the puzzles are either annoyingly obtuse or force you to backtrack to find one sticker. If there is one industry veteran who needs a rest - it's Mario.