Image tags only work for jpgs, png, gif.

Ticks are just a scaled version of seconds used because of historical reasons (timer chip in IBM PCs were set at this frequency).

time_physics is the amount of time spent calculating the new positions (CPU utilization if you want). It is _not_ related to game time or anything else.

FPS_MAX sets the frequency of display updates, PH_FPS_MAX sets the frequency of physics updates. This is easier if you think of it in terms of the inverse though: frame duration. Let's say display frame duration was 0.1 seconds (=10 fps) and physics frame duration was set to 0.01 seconds (=100 fps). In that case the physics engine gets called with a time value of 0.1 seconds and splits this into 10 tiny steps each 0.01 seconds long. At the end of these 10 steps the object is displayed at its new position.
What happens when fps_max is not a multiple of ph_fps_max ? The physics engine stores the remainder and keeps adding/subtracting from this time value in ph_fps_max duration increments. If fps_max was 0.003 threeframes would pass with physics objects not moving and the internal counter being increased to 0.003, 0.006, 0.009. In the fourth frame the value reaches 0.012, one 0.01 physics step is taken and subtracted from the counter which is now left at 0.002.