That was also true on my flight to Barcelona. The stuff that I struggled with before was suddenly much clearer. I came up with a really good optimization for the redrawing of background graphics, which allowed the game to run at a much smoother frame rate.
Just before I went on the flight I added profiling code for the bitmap drawing routines. I needed to measure how much time is spent pushing pixels. Traditionally on the C64 this is achieved by changing the screen colors to visualize the raster time used by a function.
The initial measurement was quite sobering. It looked like this:
|Drawing the flames, before optimization|