* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: 'Segoe UI', Arial, sans-serif;
  background: linear-gradient(135deg, #667eea, #764ba2);
}

.screen {
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 20px;
}

.hidden {
  display: none;
}

.card {
  background: #fff;
  border-radius: 12px;
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.25);
  padding: 32px;
  width: 320px;
}

/* Login form */
#login-form h1 {
  margin: 0 0 12px;
  text-align: center;
  color: #333;
}

#login-form .subtitle {
  text-align: center;
  color: #666;
  font-size: 14px;
  margin: 0 0 20px;
}

#login-form label {
  display: block;
  margin-bottom: 6px;
  font-size: 14px;
  color: #555;
}

#login-form input {
  width: 100%;
  padding: 10px 12px;
  margin-bottom: 16px;
  border: 1px solid #ccc;
  border-radius: 6px;
  font-size: 15px;
}

#login-form button {
  width: 100%;
  padding: 12px;
  border: none;
  border-radius: 6px;
  font-size: 15px;
  cursor: pointer;
  transition: background 0.2s;
}

#signin-btn {
  background: #667eea;
  color: #fff;
  margin-bottom: 10px;
}

#signin-btn:hover {
  background: #5563d1;
}

#signup-btn {
  background: #eee;
  color: #333;
}

#signup-btn:hover {
  background: #ddd;
}

.divider {
  display: flex;
  align-items: center;
  text-align: center;
  color: #999;
  font-size: 13px;
  margin: 18px 0 14px;
}

.divider::before,
.divider::after {
  content: '';
  flex: 1;
  border-bottom: 1px solid #ddd;
}

.divider span {
  padding: 0 10px;
}

.google-btn {
  background: #fff;
  border: 1px solid #ccc !important;
  color: #333;
}

.google-btn:hover {
  background: #f5f5f5;
}

.error {
  color: #d32f2f;
  font-size: 13px;
  min-height: 18px;
  margin: -6px 0 10px;
}

/* Calculator */
.calculator {
  width: 300px;
}

.calc-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 16px;
}

.calc-header span {
  font-size: 14px;
  color: #555;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
  max-width: 180px;
}

#logout-btn {
  border: none;
  background: #eee;
  padding: 6px 10px;
  border-radius: 6px;
  cursor: pointer;
  font-size: 13px;
}

#logout-btn:hover {
  background: #ddd;
}

#calc-display {
  width: 100%;
  padding: 14px 10px;
  font-size: 28px;
  text-align: right;
  border: 1px solid #ccc;
  border-radius: 6px;
  margin-bottom: 12px;
  background: #f7f7f7;
  color: #222;
}

.calc-buttons {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 8px;
}

.calc-buttons button {
  padding: 16px 0;
  font-size: 18px;
  border: none;
  border-radius: 6px;
  background: #f0f0f0;
  cursor: pointer;
  transition: background 0.15s;
}

.calc-buttons button:hover {
  background: #e0e0e0;
}

.calc-buttons .op {
  background: #667eea;
  color: #fff;
}

.calc-buttons .op:hover {
  background: #5563d1;
}

.calc-buttons .equals {
  background: #4caf50;
  color: #fff;
  grid-column: span 2;
}

.calc-buttons .equals:hover {
  background: #43a047;
}

.calc-buttons .zero {
  grid-column: span 1;
}