diff --git a/docs/layer-features.md b/docs/layer-features.md
index 1ec74ac..98bdf9c 100644
--- a/docs/layer-features.md
+++ b/docs/layer-features.md
@@ -49,6 +49,11 @@ Key:
     ],
     ```
 
+- branches: **optional**, determines what lines should appear on the tree when this layer is visible.
+            An array of pairs consisting of a layer name and a number from 1 to 3.
+            A branch will appear connecting this layer to the correspodnding layer, with the color based on the number.
+            You should add the branch value to the layer that is unlocked second.
+
 - style: A CSS object containing any CSS that should affect this layer's whole tab.
          Can also be a function returning a dynamic CSS object.
 
@@ -132,8 +137,5 @@ Key:
 - incr_order: **optional**, an array of layer ids. When this layer is unlocked for the first time, the "order" value
               for any not-yet-unlocked layers in this list increases. This can be used to make them harder to unlock.
 
-- branches: **optional**, determines what lines should appear on the tree when this layer is visible.
-            An array of pairs consisting of a layer name and a number from 1 to 3.
-            A branch will appear connecting this layer to the correspodnding layer, with the color based on the number.
-            You should add the branch value to the layer that is unlocked second.
-
+- should_notify: **optional**, a function to return true if this layer should be highlighted in the tree.
+                 The layer will automatically be highlighted if you can buy an upgrade whether you have this or not.
\ No newline at end of file
diff --git a/index.html b/index.html
index 8868fe8..5f26a27 100644
--- a/index.html
+++ b/index.html
@@ -45,6 +45,12 @@
 		</div>
 		<div v-if="player.tab=='changelog'" class="col right">
 			<button class="back" onclick="showTab('tree')">←</button><br>
+			<h3>v1.2.4</h3>
+			<ul>
+				<li>Layers are now highlighted if you can buy an upgrade, and a new feature, shouldNotify, lets you make it highlight other ways.</li>
+				<li>Fixed bugs with hasUpg, hasChall, hasMilestone, and inChallenge.</li>
+				<li>Changed the sample code to use the above functions for convenience.</li>
+			</ul><br>
 			<h3>v1.2.3</h3>
 			<ul>
 				<li>Added a row component, which displays a list of objects in a row.</li>
diff --git a/js/game.js b/js/game.js
index 2ee13eb..b2ba59a 100644
--- a/js/game.js
+++ b/js/game.js
@@ -5,7 +5,7 @@ var NaNalert = false;
 var gameEnded = false;
 
 let VERSION = {
-	num: "1.2.3",
+	num: "1.2.4",
 	name: "This changes everything!"
 }
 
@@ -48,9 +48,10 @@ function getPointGen() {
 
 // Function to determine if the player is in a challenge
 function inChallenge(layer, id){
-	if (player.c.active==x) return true
+	let chall = player[layer].active
+	if (chall==toNumber(id)) return true
 
-	if (layers[layer].challs[id].countsAs)
+	if (layers[layer].challs[chall].countsAs)
 		return layers[layer].challs[id].countsAs.includes(id)
 }
 
@@ -103,6 +104,23 @@ function getNextAt(layer) {
 	}
 }
 
+// Return true if the layer should be highlighted. By default checks for upgrades only.
+function shouldNotify(layer){
+	for (id in layers[layer].upgrades){
+		if (!isNaN(id)){
+			if (canAffordUpg(layer, id) && !hasUpg(layer, id) && tmp.upgrades[layer][id].unl){
+				return true
+			}
+		}
+	}
+
+	if (layers[layer].shouldNotify){
+		return layers[layer].shouldNotify()
+	}
+	else 
+		return false
+}
+
 function rowReset(row, layer) {
 	for (lr in ROW_LAYERS[row]){
 		if(layers[lr].doReset)
@@ -208,15 +226,15 @@ function canAffordUpg(layer, id) {
 }
 
 function hasUpg(layer, id){
-	return (player[layer].upgrades.includes(id))
+	return (player[layer].upgrades.includes(toNumber(id)))
 }
 
 function hasMilestone(layer, id){
-	return (player[layer].milestones.includes(id))
+	return (player[layer].milestones.includes(toNumber(id)))
 }
 
 function hasChall(layer, id){
-	return (player[layer].challs.includes(id))
+	return (player[layer].challs.includes(toNumber(id)))
 }
 
 function canAffordPurchase(layer, thing, cost) {
diff --git a/js/layers.js b/js/layers.js
index 5a8d9f6..74df6b4 100644
--- a/js/layers.js
+++ b/js/layers.js
@@ -20,8 +20,8 @@ addLayer("c", {
         canBuyMax() {}, // Only needed for static layers with buy max
         gainMult() { // Calculate the multiplier for main currency from bonuses
             mult = new Decimal(1)
-            if (player[this.layer].upgrades.includes(21)) mult = mult.times(2)
-			if (player[this.layer].upgrades.includes(23)) mult = mult.times(this.upgrades[23].currently())
+            if (hasUpg(this.layer, 166)) mult = mult.times(2)
+			if (hasUpg(this.layer, 12)) mult = mult.times(this.upgrades[12].effect())
             return mult
         },
         gainExp() { // Calculate the exponent on main currency from bonuses
@@ -83,7 +83,7 @@ addLayer("c", {
             12: {
                 desc:() => "Candy generation is faster based on your unspent Lollipops.",
                 cost:() => new Decimal(1),
-                unl() { return player[this.layer].upgrades.includes(11) },
+                unl() { return (hasUpg(this.layer, 11))},
                 effect() { // Calculate bonuses from the upgrade. Can return a single value or an object with multiple values
                     let ret = player[this.layer].points.add(1).pow(player[this.layer].upgrades.includes(24)?1.1:(player[this.layer].upgrades.includes(14)?0.75:0.5)) 
                     if (ret.gte("1e20000000")) ret = ret.sqrt().times("1e10000000")
@@ -97,7 +97,7 @@ addLayer("c", {
                 currencyDisplayName: "candies", // Use if using a nonstandard currency
                 currencyInternalName: "points", // Use if using a nonstandard currency
                 currencyLayer: "", // Leave empty if not in a layer "e.g. points"
-                unl() { return player[this.layer].upgrades.includes(12) },
+                unl() { return (hasUpg(this.layer, 12))},
                 onPurchase() { // This function triggers when the upgrade is purchased
                     player[this.layer].order = 0
                 }
@@ -192,6 +192,10 @@ addLayer("c", {
         style() {return {
             'background-color': '#3325CC'
         }},
+        shouldNotify() { // Optional, layer will be highlighted on the tree if true.
+                         // Layer will automatically highlight if an upgrade is purchasable.
+            return (player.c.buyables[11] == 1)
+        }
 })
 
 addLayer("f", {
diff --git a/js/temp.js b/js/temp.js
index 3153905..c3b2959 100644
--- a/js/temp.js
+++ b/js/temp.js
@@ -44,6 +44,7 @@ function updateTemp() {
 	if (!tmp.layerShown) tmp.layerShown = {}
 	if (!tmp.effectDescription) tmp.effectDescription = {}
 	if (!tmp.style) tmp.style = {}
+	if (!tmp.notify) tmp.notify = {}
 
 
 	for (layer in layers) {
@@ -55,6 +56,7 @@ function updateTemp() {
 		tmp.gainExp[layer] = layers[layer].gainExp()
 		tmp.resetGain[layer] = getResetGain(layer)
 		tmp.nextAt[layer] = getNextAt(layer)
+		tmp.notify[layer] = shouldNotify(layer)
 		if (layers[layer].effectDescription) tmp.effectDescription[layer] = layers[layer].effectDescription()
 
 	}
diff --git a/js/v.js b/js/v.js
index a889d70..74c3734 100644
--- a/js/v.js
+++ b/js/v.js
@@ -18,6 +18,7 @@ function loadVue() {
 				[layer]: true,
 				hidden: !tmp.layerShown[layer],
 				locked: !player[layer].unl && !tmp.layerAmt[layer].gte(tmp.layerReqs[layer]),
+				notify: tmp.notify[layer],
 				can: layerUnl(layer),
 			}"
 			v-bind:style="{