Mr. Particle Man
This is one old-school nightmare.
Particle Man, Particle Man, doing the things a particle can. What he's like is totally important since this is a review of the iOS title. It is, in fact, a sequel to the title Ms. Particle Man, which came out in 2012. It's an old-school throwback that brings the challenge in droves, while channeling Pac-Man and other arcade titles we love so much. But buyer beware: It's super difficult.
Mr. Particle Man is divided into stages that look a lot like familiar titles like Bubble Bobble or Pac-Man, with your goal being to get to the exit as quickly as you possibly can. If you get hit by something, you die. If you get sent back to the beginning of the stage, you lose your bonus. This wouldn't be so bad if you also had to contend with boss fights here and there, which impede your progress to the exit.
You also fight with maneuvering your character properly around the board, which can be quite frustrating. You must play around with momentum to make Mr. Particle Man move, and that in itself ups the challenge considerably. If you take your finger off the screen for too long, he'll also explode. There's a method to the madness, though, and finding it is half the fun.
There are over 100 stages that you'll have to trudge through, but they do end up feeling the same near the end, especially given the fact that an overwhelming amount of frustration will likely keep you from continuing when you die over and over. There's also not much going on on-screen to keep you occupied and the levels are quite drab.
Mr. Particle Man is an interesting riff on classic arcade titles, with plenty of challenge and difficulty. You may not always like where the challenge comes from, but it's there just the same, and if you can surmount it you'll find plenty to like about the game. Good luck!