The LEGO Harry Potter Years 1-4 video game app for the iPod Touch, iPad, and iPhone is pretty much exactly the same format and game play as that for the Nintendo DS, in that it's more of a Zelda-like format in which the characters go from area to area, with a slightly tilted aerial view of the players interacting with fellow characters and their atmosphere. However, if you're not used to using a console that is based solely on the touch of your fingertip to defeat adversaries and pick up clues and studs, then it becomes a bit difficult.
For those who own and are adjusted to the finger touch-and-go system of the Apple mobile equipment, it's not that difficult, but when you're trying to get away from bad guys, and worse, follow the shape of a spell in order to perform it, it because rather tedious. It came take several tries with your finger just to conjure Alohomora or Incendio because you have to match the movement of your finger with that of the spell's shape (as shown in the image above, the doorknob shape being lit up is that for Alohomora, but you have to follow it to near-perfection for it to work).
While almost everything - level and game-play wise - is exactly the same as that for the Nintendo DS, there are slight differences. As mentioned before, the way the spells are shaped is one. The DS version's of how to conjure spells are significantly easier, and for many, especially Wingardium Leviosa, the Apple version is rather unnecessarily complicated. At least with the DS the player has a thin stylus with which to follow the spell; your fingertip takes up quite a bit more screen-space, and half the time you're not entirely sure you're on the mark because your finger is completely obscuring that part of the screen. Therefore, it generally does take a few tries to get the spells going.
One mercifully good change is how Harry and Tom Riddle speak Parseltongue in the app version of the game. In the DS, the player has to 'hiss' into the microphone, and if their mic is broken, they're pretty much stuck in place. However, for the app, you simply have to click on the snake or snake-statue to speak Parseltongue, and you can continue on your journey.
At first, for a novice on an iPod Touch, iPhone, or iPad, the game can be very difficult, as you're learning how to make your character move with just the tip of your finger. With a bit a patience, you get the hang of it, and it is a rather remarkably fun game (despite the tedium of spell-casting).
The LEGO Harry Potter Years 1-4 video game for Apple iPod Touch, iPad, and iPhone, can be purchased on iTunes.