Actually really fun

Tl;dr: really fun and pretty well designed for a mobile game, though needs some time investment and patience.
Ive been playing this game for an incredibly long time, and in the end, its pretty well designed.
First, the controls. It has three modes to switch between, and youll quickly find one to suit your play style. Ive always found mobile games to have horrible controls in general, but this game doesnt infuriate me. The game tracks motions well and runs very smoothly.
In the game, your plane fires automatically; if it didnt, the game would be unplayable. You just focus on shooting enemies, dodging bullets, and collecting powerups. You can grab three types of bullets, use a screen-clearing bomber plane, and have wingmen to support fire and block a few shots. When using one bullet type, collecting a same bullet will make your shots stronger. Collecting a different bullet type switches your shot but doesnt weaken it.
Youll also collect stars to spend on new planes, wingmen, or limited use power-ups. Your first plane wont get you very far, so I recommend buying the one before the one that you unlock by beating normal. The better planes cost a ton of stars, so you should spend carefully. Also, more expensive does not necessarily mean better.
The levels have a very clean learning curve, and the difficulties are appropriate. The game of course will become easier with better planes. Also, the final boss is really fun to fight.
For all it has going for it, this game has some issues. Enemies in the later levels, most blatantly late into Hard mode, soak up way too many bullets, even with maximum firepower. Another thing is that once you reach a certain bullet power level, collecting another of the same bullet will yield a very powerful attack, but only for 10 seconds. What they should have done was make the max less powerful and let you keep it indefinitely. That would have opened up more options in design. Also with the difficulty, more difficult levels have bullets that Im convinced are impossible to dodge. For those of you who havent realized it yet, mobile games have bad controls, and getting them to work is difficult. This is a good game by those standards, but it tries too hard to be a bullet-hell game when it has no right to be one. Finally, Im going to say this: bullets that track your position and bullets that literally materialize out of nowhere are things that should NEVER be in these games.
iFighter 2 is one of the better mobile games Ive played. It has a number of issues, but it has kept me entertained for a very, very long time. It actually is cool to see what you can unlock, and most of the time the game will seem fair. It doesnt force in-app purchases on you at all, so thats another thing.

Sidescroller Def about iFighter 2: The Pacific 1942