customize playing field grid
当前为
■ Change thickness of grid lines by either increasing or decreasing the "2px".
■ Change style of grid by changing "solid" to one of 8 other options: dotted, dashed, double, groove, ridge, inset, outset, and none. Differences between all the styles can be seen in this image https://i.imgur.com/i38foDg.png
■ Change color by replacing "white" with another color, or to be more specific, replace with "rgba(255, 106, 202, 100)"
