diff --git a/src/roast.css b/src/roast.css
index 386a91b..149f30a 100644
--- a/src/roast.css
+++ b/src/roast.css
@@ -117,6 +117,14 @@ body {
     background-color: #ddd;
 }
 
+.used-temp {
+    background-color: #ccc !important;
+    color: #333;
+    border: 2px solid #888;
+    cursor: default;
+}
+
+
 #log-table {
     width: 100%;
     border-collapse: collapse;
diff --git a/src/roast.ts b/src/roast.ts
index 1a5898e..4a6c297 100644
--- a/src/roast.ts
+++ b/src/roast.ts
@@ -7,6 +7,7 @@ let targets: number[] = [];
 let currentTargetIndex = 0;
 let interval: NodeJS.Timeout | null = null;
 let firstCrackTime: number | null = null;
+let loggedTemps = new Set<number>();
 
 declare global {
   interface Window {
@@ -23,7 +24,6 @@ declare global {
   }
 }
 
-
 function startTimer(): void {
     if (isRunning) {
         alert("Timer is already running. Click again to reset.");
@@ -39,7 +39,7 @@ function startTimer(): void {
 }
 
 function stopTimer(): void {
-    if(interval !== null){
+    if (interval !== null) {
         clearInterval(interval);
     }
     isRunning = false;
@@ -48,7 +48,7 @@ function stopTimer(): void {
 function updateTimerDisplay(): void {
     const roastTimeEl = document.getElementById("roastTime")!;
     const devPercentEl = document.getElementById("devPercent")!;
-    
+
     const minutes = Math.floor(timer / 60);
     const seconds = timer % 60;
     roastTimeEl.textContent = `${minutes}:${seconds.toString().padStart(2, '0')}`;
@@ -63,11 +63,8 @@ function updateTimerDisplay(): void {
     }
 
     const timerEl = document.getElementById("timer")!;
-
-    // Reset classes
     timerEl.className = "";
 
-    // Determine phase
     if (!log.some(e => e.event === "Charge")) {
         timerEl.classList.add("initial-phase");
     } else if (!log.some(e => e.event === "Yellow")) {
@@ -75,26 +72,20 @@ function updateTimerDisplay(): void {
     } else if (firstCrackTime === null) {
         timerEl.classList.add("yellow-phase");
     } else {
-        // Development phase
         timerEl.classList.add("dev-phase");
-
         const devTime = timer - firstCrackTime;
-        const devRatio = Math.min(devTime / timer, 0.4); // clamp to 0–0.4
-
-        // Interpolate from yellow (255,255,208) to muddy brown (215,195,158)
+        const devRatio = Math.min(devTime / timer, 0.4);
         const r = Math.round(255 - devRatio * 100);
         const g = Math.round(255 - devRatio * 150);
         const b = Math.round(208 - devRatio * 125);
-
         timerEl.style.backgroundColor = `rgb(${r},${g},${b})`;
     }
-
 }
 
 function logEvent(eventName: string): void {
     if (eventName === "Charge") {
         if (log.length > 0 || isRunning) {
-            if(isRunning){
+            if (isRunning) {
                 stopTimer();
             }
             log = [];
@@ -111,8 +102,7 @@ function logEvent(eventName: string): void {
         log.push({ time: formatTime(timer), event: eventName });
         updateLog();
         document.getElementById("create-plan")!.classList.remove("hidden");
-        const tempButtons = document.getElementById("temp-buttons")!;
-        tempButtons.innerHTML = "";
+        document.getElementById("temp-buttons")!.innerHTML = "";
         updateEventButtons(eventName);
         return;
     }
@@ -125,19 +115,18 @@ function logEvent(eventName: string): void {
     updateEventButtons(eventName);
 }
 
-function updateEventButtons(eventName: string){
-    if (eventName === "Charge" || eventName === "Yellow" || eventName === "First Crack" || eventName === "Second Crack" || eventName === "Drop") {
-        const eventSequence = ["Charge", "Yellow", "First Crack", "Second Crack", "Drop"];
+function updateEventButtons(eventName: string): void {
+    const eventSequence = ["Charge", "Yellow", "First Crack", "Second Crack", "Drop"];
+    if (eventSequence.includes(eventName)) {
         const pressedIndex = eventSequence.indexOf(eventName);
-
         for (let i = 0; i <= pressedIndex; i++) {
             const btn = document.querySelector(`#event-buttons button:nth-child(${i + 1})`) as HTMLButtonElement;
             if (btn) btn.classList.add("activated");
         }
-    }
-    else if (eventName === "Reset") {
-        const eventButtons = document.querySelectorAll("#event-buttons button");
-        eventButtons.forEach(btn => btn.classList.remove("activated"));
+    } else if (eventName === "Reset") {
+        document.querySelectorAll("#event-buttons button").forEach(btn =>
+            btn.classList.remove("activated")
+        );
     }
 }
 
@@ -146,6 +135,7 @@ function resetSystem(): void {
     log = [];
     timer = 0;
     firstCrackTime = null;
+    loggedTemps.clear();
     updateLog();
     updateTimerDisplay();
 
@@ -153,12 +143,11 @@ function resetSystem(): void {
     devPercentEl.style.display = "none";
 
     const timerEl = document.getElementById("timer")!;
-    timerEl.className = "initial-phase"; // back to white background
-    timerEl.style.backgroundColor = "";  // clear inline style
+    timerEl.className = "initial-phase";
+    timerEl.style.backgroundColor = "";
 
     document.getElementById("create-plan")!.classList.remove("hidden");
-    const tempButtons = document.getElementById("temp-buttons")!;
-    tempButtons.innerHTML = "";
+    document.getElementById("temp-buttons")!.innerHTML = "";
 
     updateEventButtons("Reset");
 }
@@ -181,17 +170,24 @@ function setPlan(): void {
 function generateTempButtons(): void {
     const container = document.getElementById("temp-buttons")!;
     container.innerHTML = "";
+
     if (targets.length === 0) {
         container.innerHTML = "<p>No temperature plan set.</p>";
         return;
     }
+
     const currentTarget = targets[currentTargetIndex];
     const buttons: string[] = [];
+
     buttons.push('<button class="nav-btn" onclick="navigateTemp(-1);">&lt;&lt;</button>');
+
     for (let i = -2; i <= 2; i++) {
         const temp = currentTarget + i;
-        buttons.push(`<button onclick="logTemp(${temp})">${temp}</button>`);
+        const used = loggedTemps.has(temp);
+        const classStr = used ? 'used-temp' : '';
+        buttons.push(`<button onclick="logTemp(${temp})" class="${classStr}">${temp}</button>`);
     }
+
     buttons.push('<button class="nav-btn" onclick="navigateTemp(1);">&gt;&gt;</button>');
     container.innerHTML = buttons.join(" ");
 }
@@ -208,6 +204,7 @@ function navigateTemp(direction: number): void {
 
 function logTemp(temp: number): void {
     log.push({ time: formatTime(timer), event: "Temp", temp });
+    loggedTemps.add(temp);
     updateLog();
     currentTargetIndex++;
     if (currentTargetIndex >= targets.length) {
@@ -227,22 +224,16 @@ function updateLog(): void {
     `).join("");
 }
 
-// src/roast.ts
-
-/**
- * Generates an array of CSV strings line by line from log data.
- */
 function createCSVData(): string[] {
-  const header = "Time,Event,Temperature";
-  const logEntries = log.map(entry => `${entry.time},${entry.event}${entry.temp !== null ? `,${entry.temp}` : ''}`);
-  return [header].concat(logEntries);
+    const header = "Time,Event,Temperature";
+    const logEntries = log.map(entry =>
+        `${entry.time},${entry.event}${entry.temp !== null ? `,${entry.temp}` : ''}`
+    );
+    return [header, ...logEntries];
 }
 
-/**
- * Creates CSV format content as a single string from the array returned by createCSVData().
- */
 function generateCSVContent(): string {
-  return createCSVData().join("\n");
+    return createCSVData().join("\n");
 }
 
 function exportCSV(): void {
@@ -288,4 +279,4 @@ if (typeof window !== 'undefined') {
     window.hideGraph = hideGraph;
 }
 
-export {};
\ No newline at end of file
+export {};