/* Half-and-half rotating rainbow background */
body {
  margin: 0;
  padding: 0;
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  background: linear-gradient(to right, red 50%, orange 50%);
  background-size: 200% 100%;
  animation: rainbowHalf 10s linear infinite;
  color: #333;
  display: flex;
  justify-content: center;
  min-height: 100vh;
  align-items: center;
}

/* Rainbow rotation animation with lighter colors */
@keyframes rainbowHalf {
  0%   { background: linear-gradient(to right, #ffb3ba 50%, #ffe0b3 50%); }
  14%  { background: linear-gradient(to right, #ffe0b3 50%, #ffffba 50%); }
  28%  { background: linear-gradient(to right, #ffffba 50%, #baffc9 50%); }
  42%  { background: linear-gradient(to right, #baffc9 50%, #bae1ff 50%); }
  57%  { background: linear-gradient(to right, #bae1ff 50%, #b3baff 50%); }
  71%  { background: linear-gradient(to right, #b3baff 50%, #e1b3ffd3 50%); }
  85%  { background: linear-gradient(to right, #e1b3ffc5 50%,#ffb3ba 50%); }
  100% { background: linear-gradient(to right, #ffb3ba 50%, #ffe0b3 50%); }
}

.container {
  max-width: 700px;
  margin: 40px;
  background-color: #ffffffa8; /* semi-transparent for rainbow to show */
  border-radius: 15px;
  padding: 25px;
  box-shadow: 0 8px 25px rgba(0, 0, 0, 0.15);
  width: 100%;
  box-sizing: border-box;
  text-align: center;
}

h1 {
  font-weight: 700;
  font-size: 26px;
  margin-bottom: 25px;
  color: #1b1b1b;
}

.tab-buttons {
  margin-bottom: 25px;
}

.tab-btn {
  background: white;
  border: 2px solid #92f596;
  color: #94f697;
  padding: 10px 20px;
  margin: 0 10px;
  border-radius: 30px;
  font-weight: 600;
  cursor: pointer;
  transition: 0.3s ease;
}

.tab-btn.active,
.tab-btn:hover {
  background: #97fa9b;
  color: white;
  box-shadow: 0 0 12px #87f28b;
}

.tab-section {
  display: block;
  text-align: left;
}

.hidden {
  display: none;
}

label {
  display: block;
  margin-bottom: 6px;
  font-weight: 600;
  font-size: 16px;
}

input[type='number'],
select {
  width: 100%;
  padding: 10px;
  margin-bottom: 15px;
  border-radius: 12px;
  border: 1px solid #ccc;
  font-size: 16px;
  box-sizing: border-box;
}

.generate-btn,
#calcSgpaBtn,
#calcCgpaBtn {
  display: block;
  margin: 10px auto;
  background: #97fa9b;
  color: white;
  border: none;
  padding: 14px 35px;
  font-weight: 700;
  border-radius: 50px;
  cursor: pointer;
  font-size: 18px;
  box-shadow: 0 6px 12px rgba(76, 227, 81, 0.5);
  transition: background 1000s;
}

.generate-btn:hover,
#calcSgpaBtn:hover,
#calcCgpaBtn:hover {
  background: #388e3c;
}

.subject-row,
.semester-row {
  display: flex;
  gap: 12px;
  margin-bottom: 15px;
  align-items: center;
}

.subject-row select,
.subject-row input,
.semester-row input {
  flex: 1;
  padding: 10px;
  border-radius: 12px;
  border: 1px solid #ccc;
  font-size: 16px;
}

.result {
  margin-top: 20px;
  font-size: 22px;
  font-weight: 700;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 12px;
  color: #1b5e20;
}

.result .emoji {
  font-size: 30px;
}

/* ✅ Responsive fixes for mobile */
@media (max-width: 600px) {
  .container {
    margin: 20px;
    padding: 15px;
  }

  .tab-buttons {
    display: flex;
    flex-direction: column;
    gap: 10px;
  }

  .tab-btn {
    margin: 0;
    width: 100%;
  }

  .subject-row,
  .semester-row {
    flex-wrap: wrap;
  }

  .subject-row select,
  .subject-row input,
  .semester-row input {
    flex: 1 1 100%;
  }
}