Based on the TV series; My Little Pony: Friendship is Magic
Rescue the trapped ponies by completing the puzzle in each level. As you progress through the game and rescue more ponies, they can all work together to solve the more difficult levels. Each pony has an ability. Many of these show up in this game, but if they don't they will appear in subsequent games:
Twilight Sparkle can read the spells placed throughout some levels;
Rainbow Dash can stay continuously airborne (she floats away alot)
Applejack can smash glass windows in your way;
Fluttershy can speak to animals in the level and they will help you in some way;
Pinkie Pie activates and moves party cannons that can shoot into spaces too small for the ponies to fit through;
Rarity can collect jewels without breaking them.
There are also three different colored portals that only ponies of a certain species can pass through. And you can use magic to move many objects by clicking on them and then using the keypad.
Good Luck!