html, body {
  height: 100%;
  margin: 0;
  padding: 0;
}
body {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}
.container {
  flex: 1 0 auto;
  max-width: 540px;      /* 這裡控制版心最大寬度，建議 480～600px */
  margin: 30px auto 0px auto;     /* 水平自動置中，上下留白 */
  background: #fff;
  border-radius: 20px;
  box-shadow: 0 0 16px #e2e8f0;
  padding: 32px 24px;
}
footer {
  flex-shrink: 0;
  text-align: center;
  font-size: 1rem;
  color: #888;
  margin-top: 30px;
}
h1, h2 {
  text-align: center;
}
input, button, select, textarea {
  font-size: 1.18rem;
  padding: 10px;
  border-radius: 10px;
  border: 1px solid #cbd5e1;
  margin: 8px 0;
}
button {
  background: #38bdf8;
  color: #fff;
  border: none;
  cursor: pointer;
  transition: background 0.2s;
  margin: 0 10px 0 0;
  padding: 12px 40px;
  font-size: 1.22rem;
  border-radius: 14px;
  font-weight: 500;
}
button:last-child {
  margin-right: 0;
}
button:hover {
  background: #0ea5e9;
}
.button-row {
  display: flex;
  justify-content: center;
  gap: 16px;
  margin: 18px 0 16px 0;
}
.button-row button {
  min-width: 240px; /* 建議120~160px，看你覺得舒服 */
}
.student-list, .answer-list {
  width: 100%;
  border-collapse: collapse;
  margin-top: 18px;
}
.student-list th, .student-list td, .answer-list th, .answer-list td {
  border: 1px solid #d1d5db;
  padding: 8px 4px;
  text-align: center;
}
.status-wait {
  color: #f59e42;
  font-weight: bold;
}
.status-correct {
  color: #16a34a;
  font-weight: bold;
}
.status-wrong {
  color: #dc2626;
  font-weight: bold;
}
.status-noanswer {
  color: #f59e42;
  font-weight: bold;
}
.center {
  text-align: center !important;
}
.big-title {
  font-size: 2.4rem;
  font-weight: 700;
  margin-bottom: 12px;
}
.big-status {
  font-size: 2rem;
  font-weight: bold;
  margin: 18px 0 0 0;
}
.big-time {
  font-size: 2.8rem;
  color: #ef4444;
  font-weight: bold;
  margin-top: 10px;
}
.big-alert {
  font-size: 2.2rem;
  color: #ef4444;
  font-weight: bold;
  margin-top: 12px;
}
.question-box {
  font-size: 2.8rem;
  font-weight: bold;
  border: 3px solid #222;
  display: inline-block;
  padding: 14px 32px;
  margin: 24px 0 14px 0;
  border-radius: 10px;
  letter-spacing: 8px;
  background: #fff;
  user-select: none;
  -webkit-user-select: none;
  -moz-user-select: none;
  -ms-user-select: none;
  cursor: default;
}
.name-line {
  font-size: 1.4rem;
  margin-bottom: 8px;
}
.name-big {
  font-size: 2.1rem;
  font-weight: bold;
  color: #222;
  border-bottom: 2px solid #ddd;
  padding: 0 10px;
}
#studentPanel .button-row {
  margin-bottom: 12px;
  margin-top: 0;
}
.input-large {
  font-size: 2.2rem !important;
  padding: 14px 32px !important;
  width: auto !important;
  min-width: 340px;
  max-width: 90%;
  box-sizing: border-box;
  margin-top: 16px;
  margin-bottom: 16px;
  text-align: center;
  display: block;
  margin-left: auto;
  margin-right: auto;
}
@media (max-width: 600px) {
  .question-box, .input-large { font-size: 1.5rem !important; min-width: 140px; }
  .container {
    max-width: 100vw;
    border-radius: 0;
    margin: 0;
    box-shadow: none;
    padding: 10px 0;
  }
}
.mt-2x { margin-top: 12px !important; }
.mt-lg { margin-top: 32px !important; }