Only add/remove upgrade classes if needed.

The last state of the upgrade buttons are now cached. This ensures that
the classList is perturbed *only* if this would actually change the
appearance, and seems to be far faster than just adding something
to the classList over and over

gorge.js

@@ -309,6 +309,7 @@ function switchShowOwnedUpgrades() {
 function displayUpgrades(owned) {
   if (owned) {
     Object.entries(ownedUpgrades).forEach(([key, val]) => {
+
       let button = cache.upgradeButtons[key];
       if (val) {
         button.classList.remove("hidden");
@@ -320,20 +321,29 @@ function displayUpgrades(owned) {
   else {
     for (let id of remainingUpgrades) {
       let button = cache.upgradeButtons[id];
+      let visible = states.upgrades[id].visible;
+      let available = states.upgrades[id].available;
 
-      if (ownedUpgrades[id]) {
+      if (ownedUpgrades[id] && visible !== false) {
         button.classList.add("hidden");
+        states.upgrades[id].visible = false;
         continue;
       }
-      if (upgradeReachable(id)) {
+
+      if (upgradeReachable(id) && visible !== true) {
         button.classList.remove("hidden");
-      } else {
+        states.upgrades[id].visible = true;
+      } else if (!upgradeReachable(id) && visible !== false) {
         button.classList.add("hidden");
+        states.upgrades[id].visible = false;
       }
-      if (upgradeAvailable(id)) {
+
+      if (upgradeAvailable(id) && available !== true) {
         button.classList.remove("upgrade-button-inactive");
-      } else {
+        states.upgrades[id].available = true;
+      } else if (!upgradeAvailable(id) && available !== false) {
         button.classList.add("upgrade-button-inactive");
+        states.upgrades[id].available = false;
       }
     }
 
@@ -419,6 +429,7 @@ function setup() {
   load();
   unlockAtStart();
   initializeCaches();
+  initializeStates();
   updateAll();
 
 }
@@ -453,6 +464,25 @@ function initializeCaches() {
   cache.upgradeButtons = upgradeButtons;
 }
 
+const states = {};
+
+// we can keep track of some things, like whether
+// specific upgrades are currently visible. this
+// way, we don't have to set them visible every tick;
+// we can just check if they've been handled already
+
+function initializeStates() {
+  const upgradeStates = {};
+
+  Object.keys(upgrades).forEach(key => {
+    upgradeStates[key] = {
+      visible: undefined,
+      available: undefined
+    }
+  });
+
+  states.upgrades = upgradeStates;
+}
 function unlockAtStart() {
   unlockBuilding("micro");