line_collision(x1,y1,x2,y2,x3,y3,x4,y4)

--https://gamedev.stackexchange.com/questions/26004/how-to-detect-2d-line-on-line-collision
function line_collision(x1,y1,x2,y2,x3,y3,x4,y4)

denominator= ((x2 - x1) * (y4 - y3)) - ((y2 - y1) * (x4 - x3));
numerator1 = ((y1 - y3) * (x4 - x3)) - ((x1 - x3) * (y4 - y3));
numerator2 = ((y1 - y3) * (x2 - x1)) - ((x1 - x3) * (y2 - y1));

--// Detect coincident lines
if (denominator == 0) then
  return (numerator1 == 0 and numerator2 == 0)
else
  r = numerator1 / denominator;
  s = numerator2 / denominator;
  return ((r >= 0 and r <= 1) and (s >= 0 and s <= 1));
end
end