Upgrades have prerequisites. The game only checks for upgrades that are not owned

constants.js

@@ -119,6 +119,11 @@ const upgrades = {
     "effect": {
       "type": "prod-2x",
       "target": "micro"
+    },
+    "prereqs": {
+      "buildings": {
+        "micro": 1
+      }
     }
   },
   "micro-prod-2": {
@@ -130,6 +135,11 @@ const upgrades = {
     "effect": {
       "type": "prod-2x",
       "target": "micro"
+    },
+    "prereqs": {
+      "buildings": {
+        "micro": 10
+      }
     }
   }
 }

gorge.js

@@ -4,6 +4,8 @@ let belongings = {};
 
 let ownedUpgrades = {};
 
+let remainingUpgrades = [];
+
 let resources = {};
 
 let updateRate = 60;
@@ -25,7 +27,6 @@ function productivityOf(type) {
     if (!ownedUpgrades[key]) {
       continue;
     }
-    console.log(value);
     if (value.effect.type == "prod-2x") {
       if (value.effect.target == key) {
         baseProd *= 2;
@@ -105,19 +106,27 @@ function spend(cost) {
 }
 
 function displayUpgrades() {
-  for (const [key, value] of Object.entries(upgrades)) {
-    let button = document.querySelector("#upgrade-" + key);
+  for (let id of remainingUpgrades) {
+    let button = document.querySelector("#upgrade-" + id);
 
-    if (ownedUpgrades[key]) {
+    if (ownedUpgrades[id]) {
       button.style.display = "none";
-      return;
+      continue;
     }
-    if (canAfford(upgrades[key].cost)) {
+    if (upgradeAvailable(id)) {
       button.classList.remove("upgrade-button-inactive");
     } else {
       button.classList.add("upgrade-button-inactive");
     }
   }
+
+  // now we throw out stuff
+
+  for (let i = remainingUpgrades.length-1; i >= 0; i--) {
+    if (ownedUpgrades[remainingUpgrades[i]]) {
+      remainingUpgrades.splice(i, 1);
+    }
+  }
 }
 
 function buyUpgrade(id) {
@@ -195,10 +204,35 @@ function createBuildings() {
   }
 }
 
+function upgradeAvailable(id) {
+  if (ownedUpgrades[id]) {
+    return false;
+  }
+
+  if (!canAfford(upgrades[id].cost)) {
+    return false;
+  }
+
+  for (const [type, reqs] of Object.entries(upgrades[id].prereqs)) {
+    if (type == "buildings") {
+      for (const [building, amount] of Object.entries(upgrades[id].prereqs[type])) {
+        if (belongings[building].count < amount) {
+          return false;
+        }
+      }
+    }
+  }
+
+  return true;
+}
+
 function createUpgrades() {
   let container = document.querySelector("#upgrades-list");
 
   for (const [key, value] of Object.entries(upgrades)) {
+
+    remainingUpgrades.push(key);
+
     let button = document.createElement("div");
     button.classList.add("upgrade-button");
     button.id = "upgrade-" + key;