For one, testing mechanisms individually really doesn't work as it gives an unrealistic view of the situation.
By way of example, testing the "to hit" mechanism devoid of any mechanism for chance events and enemy return fire had convinced me that the mechanism was flawed. However, when I started to add those in, I was seeing a very different picture.
Another problem is that I had made the creative process very mechanical.
This works for some, I suppose, but I prefer a more organic, free-form approach to creative activities . And so last night, I threw out my work so far, broke out my WWII USMC (just 3 of them) and Japanese (quite a few more) and made it up as I went, as I would any other time I felt like having a game without spending part of that game looking up a forgotten rule. The result is that I feel like I'm closer to having a basic structure for the game that incorporates all of the elements I wanted (excluding the "advanced" or "optional" ideas).
I'll have no time to work on the game today and tomorrow is looking unlikely as well. But, as I'm feeling a bit of chest congestion coming on, and only 21 days left, I may opt to turn my day out playing Call of Cthulhu,drinking highly caffeinated beverages and eating Twizzlers, into a day in working on my game, drinking tea and eating Twizzlers (you didn't think I'd give up my candy treat did you?).