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HTML 

              
                <!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Caffeine Analyzer</title>
  <link rel="stylesheet" href="style.css">
</head>
<body>
  <div class="container">
    <a 
      href="https://calculator.institute/caffeine-half-life-calculator-tool/" 
      class="calculator-button" 
      target="_blank" 
      rel="noopener noreferrer"
    >
      Caffeine Half Life Calculator
    </a>
    <h1>Caffeine Analyzer</h1>
    <p>Use this tool to analyze your daily caffeine intake and its impact.</p>
    
    <form id="caffeine-form">
      <label for="drink">Type of Drink:</label>
      <select id="drink" name="drink">
        <option value="coffee">Coffee (95mg per cup)</option>
        <option value="tea">Tea (47mg per cup)</option>
        <option value="soda">Soda (39mg per can)</option>
        <option value="energy">Energy Drink (80mg per can)</option>
      </select>

      <label for="quantity">Number of Servings:</label>
      <input type="number" id="quantity" name="quantity" min="1" placeholder="Enter quantity">

      <button type="button" onclick="analyzeCaffeine()">Analyze</button>
    </form>

    <div id="result"></div>
  </div>
  <script src="script.js"></script>
</body>
</html>
!

CSS 

              
                body {
  font-family: Arial, sans-serif;
  margin: 0;
  padding: 0;
  background-color: #f4f4f9;
  color: #333;
}

.container {
  max-width: 600px;
  margin: 50px auto;
  padding: 20px;
  background: #fff;
  border-radius: 8px;
  box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
  text-align: center;
}

h1 {
  font-size: 24px;
  margin-bottom: 20px;
}

p {
  font-size: 16px;
  margin-bottom: 20px;
}

label {
  display: block;
  margin: 10px 0 5px;
}

input, select {
  width: 100%;
  padding: 10px;
  margin-bottom: 20px;
  border: 1px solid #ccc;
  border-radius: 4px;
}

button {
  background-color: #007bff;
  color: #fff;
  border: none;
  padding: 10px 15px;
  border-radius: 4px;
  cursor: pointer;
}

button:hover {
  background-color: #0056b3;
}

.calculator-button {
  display: inline-block;
  background-color: #28a745;
  color: #fff;
  padding: 15px 20px;
  border: none;
  border-radius: 5px;
  font-size: 16px;
  cursor: pointer;
  margin-bottom: 20px;
}

.calculator-button:hover {
  background-color: #218838;
}

#result {
  font-size: 18px;
  margin-top: 20px;
  color: #555;
}
!

JS 

              
                function analyzeCaffeine() {
  const drink = document.getElementById("drink").value;
  const quantity = parseInt(document.getElementById("quantity").value);

  if (!quantity || quantity <= 0) {
    alert("Please enter a valid quantity!");
    return;
  }

  let caffeineContent = 0;

  switch (drink) {
    case "coffee":
      caffeineContent = 95;
      break;
    case "tea":
      caffeineContent = 47;
      break;
    case "soda":
      caffeineContent = 39;
      break;
    case "energy":
      caffeineContent = 80;
      break;
    default:
      caffeineContent = 0;
  }

  const totalCaffeine = caffeineContent * quantity;
  let message = `You consumed ${totalCaffeine} mg of caffeine.`;

  if (totalCaffeine > 400) {
    message += " This is above the recommended daily limit. Please reduce your intake!";
  } else {
    message += " This is within the safe daily limit. Keep it balanced!";
  }

  document.getElementById("result").innerHTML = message;
}
!
999px

Console