#define TURN_TIME   85

int move_time;              // define a variable

task main()
{
  move_time = 20;           // set the initial value
  repeat(50)
  {
    OnFwd(OUT_A+OUT_C);
    Wait(move_time);       // use the variable for sleeping
    OnRev(OUT_C);
    Wait(TURN_TIME);
    move_time += 5;         // increase the variable
  }
  Off(OUT_A+OUT_C);
}