It's a departure from my two previous games, Reversi and Merelles, which were both abstract strategy games. Magnetic Block Puzzle is, as the name implies, a puzzle game. The aim of each of the 110 puzzles is to join the coloured blocks, which are special magnets that only stick to other blocks of the same colour, by tilting the puzzle to make the blocks move.
The process of building this game, from inception to completion, went something like this:
I started out this project by building the underlying model of the blocks and the board, including the logic to shift the blocks around. This was done in a test-driven manner, which helped to drive out the model and behaviour correctly and to identify edge and corner cases early. Towards the end of this process, I discovered a similar puzzle game on clickmazes.com and contacted them to ensure I wouldn't be violating a copyright. They were happy for me to proceed and gave me permission to use two of their puzzles too.
The next step was to build a solver and a puzzle builder application on top of the model, to allow me to design and test puzzle layouts. This was done as an iPhone application and many puzzles were designed on my iPhone whilst I was riding on the London Underground :)
Once enough puzzles had been designed, I tailored the solver to determine various things about each puzzle such as the number of solutions, the number of moves in the best solution, the number of useful positions in the solution tree (positions from which the puzzle can be solved), the number of dead-end positions (positions from which the puzzle cannot be solved), and so on. This proved to be quite CPU-intensive on the more complex puzzles, so it was compiled and run on my Mac rather than on the iPhone. These values were then used to assess the relative difficulty of each puzzle.
Every puzzle included in the game was thus designed by hand, but assessed and verified by code.
Finally I wrote the actual application, including in it the 110 puzzles that had been selected for the final application, in a local SQLite database. Like the solver and the puzzle builder, the actual game was built on top of the model built initially.
I started this application in early December 2008 and finished it in late April 2009 - nearly five months of much of my free time went into building it. I am happy with the end product and hope that those who purchase it enjoy playing it as much as I enjoyed creating it. It's available on the App Store now.