line 36, #define M_GRAV 6.67300e-1 // Edit this to change max gravity.
line 50, #define XRES 612 // Edit this to change the width of TPT's play area.
line 51, #define YRES 384 // Edit this to change the height of TPT's play area.
line 69, #define CELL 4 // Edit this to change the wall block's size(currently 4x4 = CELL*CELL)