Add knobbed plate

Lego.json

@@ -25,6 +25,11 @@
             "studs_x": "6",
             "studs_y": "6"
         },
+        "Plate_10x2": {
+            "type": "plate",
+            "studs_x": "10",
+            "studs_y": "2"
+        },
         "Plate_4x2": {
             "type": "plate",
             "studs_x": "4",
@@ -49,6 +54,11 @@
             "type": "slope45",
             "studs_x": "2",
             "studs_y": "1"
+        },
+        "Knob_2x2": {
+            "type": "knob",
+            "studs_x": "2",
+            "studs_y": "2"
         }
     },
     "fileFormatVersion": "1"

Lego.scad

@@ -1,5 +1,5 @@
 /* [Lego Type] */
-type = "brick"; // ["brick":Brick, "plate":Plate, "slope45":"Slope 45"]
+type = "brick"; // ["brick":Brick, "plate":Plate, "slope45":"Slope 45","knob":Knob]
 studs_x = 4;
 studs_y = 2;
 slice_x = false;
@@ -7,25 +7,39 @@ slice_x = false;
 /* [Hidden] */
 block_height =
 	(type == "brick" || type == "slope45") ? 9.6 :
-	type == "plate" ? 3.2 :
+	(type == "plate" || type == "knob") ? 3.2 :
 	0;
 length_per_stud = 31.8 / 4;
 wall_width = 1.6;
 ceiling_width = 1;
+centered_knob = type == "knob";
 $fs = 1;
 
 assert(block_height > 0, "Invalid block height. Perhaps type is not correct?");
 assert(studs_x >= studs_y, "studs_x must be equal or larger than studs_y");
 
 module stud() {
+	if (type == "knob") {
+		difference() {
 			cylinder(d = 4.8, h = 1.8);
+			cylinder(d = 3.2, h = 1.9);
+		}
+	} else {
+		cylinder(d = 4.8, h = 1.8);
+	}
 }
 
 module studs() {
+	if (centered_knob) {
+		for (x = [0:studs_x-2], y = [0:studs_y-2])
+		translate([(x+1) * length_per_stud, (y+1) * length_per_stud, 0])
+		stud();
+	} else {
 		for (x = [0:studs_x-1], y = [0:studs_y-1])
 		translate([(x+0.5) * length_per_stud, (y+0.5) * length_per_stud, 0])
 		stud();
 	}
+}
 
 module base() {
 	width = (studs_y + (type == "slope45" ? 1 : 0)) * length_per_stud;
@@ -50,7 +64,7 @@ module base() {
 }
 
 module pillar() {
-	cylinder(h = block_height, d = 6.48);
+	cylinder(h = block_height, d = 6.55);
 }
 
 module small_pillar() {