Add simple coaster

coaster.scad

@@ -0,0 +1,17 @@
+Diameter = 101.6; // 0.1
+Depth = 6; // 0.1
+
+Inset = false;
+Inset_depth = 4; // 0.1
+Inset_width = 5; // 0.1
+
+$fn = 180; // 0.1
+
+rotate([0, 180, 0]) {
+difference() {
+cylinder(h = Depth, d = Diameter); 
+if (Inset) {
+    cylinder(h = Inset_depth, d = Diameter - 2*Inset_width);
+};
+};
+};