Add sandbox building, restructure levels, show pinned shapes in constant signal dialog

src/js/game/systems/item_producer.js

@@ -0,0 +1,24 @@
+import { ItemProducerComponent } from "../components/item_producer";
+import { GameSystemWithFilter } from "../game_system_with_filter";
+
+export class ItemProducerSystem extends GameSystemWithFilter {
+    constructor(root) {
+        super(root, [ItemProducerComponent]);
+    }
+
+    update() {
+        for (let i = 0; i < this.allEntities.length; ++i) {
+            const entity = this.allEntities[i];
+            const pinsComp = entity.components.WiredPins;
+            const pin = pinsComp.slots[0];
+            const network = pin.linkedNetwork;
+
+            if (!network || !network.hasValue()) {
+                continue;
+            }
+
+            const ejectorComp = entity.components.ItemEjector;
+            ejectorComp.tryEject(0, network.currentValue);
+        }
+    }
+}