//walls are red
translate ([0, -1, 0]) 
	cube([20, 2, 7.5]);
translate ([0, 19, 0]) 
	cube([20, 2, 7.5]);
translate ([-1, 0, 0]) 
	cube([2, 20, 7.5]);
translate ([19, 0, 0]) 
	cube([2, 20, 7.5]);