<!DOCTYPE html>
<html lang="th">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>การคำนวณคะแนนและเกรด</title>
  <style>
    * {
      box-sizing: border-box;
    }
    body {
      font-family: 'Arial', sans-serif;
      background-color: #f9f9f9;
      margin: 0;
      padding: 0;
      display: flex;
      justify-content: center;
      align-items: center;
      min-height: 100vh;
    }
    .container {
      background-color: #ffffff;
      width: 90%;
      max-width: 600px;
      padding: 25px;
      border-radius: 10px;
      box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
    }
    h1 {
      text-align: center;
      color: #2c3e50;
    }
    .input-group {
      margin: 15px 0;
      display: flex;
      justify-content: space-between;
      align-items: center;
    }
    .input-group label {
      flex: 1;
      font-size: 16px;
      color: #333;
    }
    .input-group input {
      flex: 2;
      padding: 10px;
      font-size: 16px;
      border: 1px solid #ddd;
      border-radius: 5px;
    }
    .button-container {
      text-align: center;
      margin-top: 20px;
    }
    button {
      background-color: #3498db;
      color: white;
      border: none;
      padding: 12px 20px;
      font-size: 16px;
      border-radius: 5px;
      cursor: pointer;
    }
    button:hover {
      background-color: #2980b9;
    }
    .result {
      margin-top: 20px;
      text-align: center;
      font-size: 18px;
    }
    table {
      width: 100%;
      border-collapse: collapse;
      margin-top: 20px;
    }
    th, td {
      padding: 10px;
      text-align: center;
      border: 1px solid #ddd;
    }
    th {
      background-color: #3498db;
      color: white;
    }
  </style>
</head>
<body>
  <div class="container">
    <h1>กรอกคะแนนและคำนวณเกรด</h1>
    <form method="post">
      <div class="input-group">
        <label>จิตพิสัย:</label>
        <input type="number" name="participation" placeholder="กรอกคะแนน" required min="0" max="100">
      </div>
      <div class="input-group">
        <label>งาน:</label>
        <input type="number" name="assignment" placeholder="กรอกคะแนน" required min="0" max="100">
      </div>
      <div class="input-group">
        <label>สอบกลางภาค:</label>
        <input type="number" name="midterm" placeholder="กรอกคะแนน" required min="0" max="100">
      </div>
      <div class="input-group">
        <label>สอบปลายภาค:</label>
        <input type="number" name="final" placeholder="กรอกคะแนน" required min="0" max="100">
      </div>
      <div class="button-container">
        <button type="submit">คำนวณคะแนน</button>
      </div>
    </form>

    <?php
    if ($_SERVER["REQUEST_METHOD"] == "POST") {
        $participation = $_POST["participation"];
        $assignment = $_POST["assignment"];
        $midterm = $_POST["midterm"];
        $final = $_POST["final"];

        $totalScore = $participation + $assignment + $midterm + $final;

        function calculateGrade($score) {
            if ($score >= 80) return "A";
            if ($score >= 75) return "B+";
            if ($score >= 70) return "B";
            if ($score >= 65) return "C+";
            if ($score >= 60) return "C";
            if ($score >= 55) return "D+";
            if ($score >= 50) return "D";
            return "F";
        }

        $grade = calculateGrade($totalScore);

        echo "<div class='result'>";
        echo "<p>คะแนนรวม: $totalScore</p>";
        echo "<p>เกรดที่ได้: $grade</p>";
        echo "</div>";
    }
    ?>
  </div>
</body>
</html>