// After page loading, if the swap images are preloaded, mouse-over on a cell // will immediately show the swap image, instead of momentarily handing for the swap image to be loaded. // To test if preloading is working, delete the temporary cach file of the browser, // quit the browser, re-open the browser, go to project page and move the mouse over a large cell (2x2) // to see if there is any delay in loading the swap image. // Colored rectangle background for each main menu // Their positions, colors are defined in the style sheet.