After deciding on the game I wanted to develop, the first major decision was: do I use OpenGL or not?

I have absolutely no experience in OpenGL, but was prepared to slog through learning it. I really did not want to use it if I did not have to, though.

My requirements for the game were:
- Drag a square from a "tray" area to the game board and double-tap to place it
- Rotate the square in 90 degree increments
- Animate tokens along a pre-calculated path made of lines, arcs, and curves

So, I looked through the view and animation APIs, and I bought the 3 available books on iPhone programming. It looked like I would not have to learn OpenGL. The trickiest part would be doing the animation along a path, since rotating a view is fairly straightforward. From the docs, it looked like the CGAnimation class had what I needed, and it turned out that it works great for me.

So, one major design decision down, and a sigh of relief from me, because I would not have to learn OpenGL for this game.

For anyone interested in writing a game for the iPhone, I thought that I'd try to journal some of my experiences developing Pathology.

My sons and I regularly play board games with friends, and someone brought in a game called Tsuro, which my sons really enjoyed playing. I took a look at the game, saw how simple the rules are, combined with deceptive strategy and depth, and I thought "This would be cool to play on the iPhone." I had also been looking into the iPhone APIs and I saw a good fit. I could leverage animation along a path as well as touch/drag, and the core of the game was born in my head.