/* ============================================
   COLLEGE TOOLKIT — Premium Design System
   Single consolidated stylesheet
   ============================================ */

/* --- 1. VARIABLES & THEMING --- */
:root {
  --fs-h1: clamp(1.6rem, 4vw, 2.4rem);
  --fs-h2: clamp(1.3rem, 3vw, 1.8rem);
  --fs-body: clamp(0.95rem, 2vw, 1.05rem);
  --fs-small: 0.82rem;
  --radius: 18px;
  --radius-sm: 12px;
  --radius-full: 100px;

  /* Light theme */
  --bg: #f0f2f5;
  --surface: rgba(255,255,255,0.72);
  --surface-solid: #ffffff;
  --surface-hover: rgba(255,255,255,0.9);
  --text: #1a1a2e;
  --text-dim: #555770;
  --border: rgba(0,0,0,0.08);
  --glow: rgba(99,102,241,0.15);

  /* Accent */
  --accent: #6366f1;
  --accent-light: #a5b4fc;
  --accent-surface: rgba(99,102,241,0.08);
  --accent-on: #ffffff;
  --success: #10b981;
  --success-surface: rgba(16,185,129,0.1);
  --warning: #f59e0b;
  --warning-surface: rgba(245,158,11,0.1);
  --danger: #ef4444;
}

[data-theme="dark"] {
  --bg: #0f0f1a;
  --surface: rgba(30,30,50,0.7);
  --surface-solid: #1a1a2e;
  --surface-hover: rgba(40,40,65,0.85);
  --text: #eaeaf0;
  --text-dim: #9ca3af;
  --border: rgba(255,255,255,0.06);
  --glow: rgba(99,102,241,0.25);
  --accent: #818cf8;
  --accent-light: #6366f1;
  --accent-surface: rgba(129,140,248,0.12);
}

/* Color themes */
[data-color="blue"]  { --accent: #3b82f6; --accent-light: #93c5fd; --accent-surface: rgba(59,130,246,0.1); --glow: rgba(59,130,246,0.2); }
[data-color="red"]   { --accent: #ef4444; --accent-light: #fca5a5; --accent-surface: rgba(239,68,68,0.1); --glow: rgba(239,68,68,0.2); }
[data-color="green"] { --accent: #10b981; --accent-light: #6ee7b7; --accent-surface: rgba(16,185,129,0.1); --glow: rgba(16,185,129,0.2); }
[data-theme="dark"][data-color="blue"]  { --accent: #60a5fa; --accent-light: #3b82f6; }
[data-theme="dark"][data-color="red"]   { --accent: #f87171; --accent-light: #ef4444; }
[data-theme="dark"][data-color="green"] { --accent: #34d399; --accent-light: #10b981; }

/* --- 2. RESET & BASE --- */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
body {
  font-family: 'Inter', system-ui, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  min-height: 100vh;
  transition: background 0.4s, color 0.3s;
  overflow-x: hidden;
}

/* Animated mesh gradient background */
body::before {
  content: '';
  position: fixed;
  inset: 0;
  z-index: -1;
  background:
    radial-gradient(ellipse 60% 50% at 20% 20%, var(--glow), transparent),
    radial-gradient(ellipse 50% 40% at 80% 80%, rgba(236,72,153,0.08), transparent),
    radial-gradient(ellipse 40% 60% at 50% 50%, rgba(14,165,233,0.06), transparent);
  animation: meshDrift 20s ease-in-out infinite alternate;
}
@keyframes meshDrift {
  0%   { filter: hue-rotate(0deg); }
  100% { filter: hue-rotate(30deg); }
}

/* --- 3. HEADER --- */
.app-header {
  background: var(--surface);
  backdrop-filter: blur(20px) saturate(1.4);
  -webkit-backdrop-filter: blur(20px) saturate(1.4);
  border-bottom: 1px solid var(--border);
  padding: 1.25rem 1.5rem 0;
  position: sticky; top: 0; z-index: 100;
}
.header-content {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 0.75rem;
  max-width: 680px;
  margin: 0 auto;
}
.titles h1 {
  font-size: var(--fs-h1);
  font-weight: 800;
  letter-spacing: -0.5px;
  line-height: 1.15;
  background: linear-gradient(135deg, var(--accent), var(--accent-light));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}
.titles p { font-size: var(--fs-small); color: var(--text-dim); }

.controls {
  display: flex;
  gap: 0.5rem;
  align-items: center;
}
.controls select {
  padding: 0.4rem 0.6rem;
  border-radius: var(--radius-sm);
  background: var(--surface-solid);
  color: var(--text);
  border: 1px solid var(--border);
  font: inherit;
  font-size: var(--fs-small);
  cursor: pointer;
  outline: none;
  transition: border-color 0.2s;
}
.controls select:focus { border-color: var(--accent); }

.icon-btn {
  background: transparent;
  border: none;
  color: var(--text);
  width: 36px; height: 36px;
  border-radius: 50%;
  display: grid;
  place-items: center;
  cursor: pointer;
  transition: background 0.2s, transform 0.2s;
}
.icon-btn:hover { background: var(--accent-surface); transform: scale(1.1); }
.icon-btn svg { width: 20px; height: 20px; }

/* Nav */
.app-nav {
  display: flex;
  gap: 0;
  margin-top: 1rem;
  max-width: 680px;
  margin-left: auto;
  margin-right: auto;
}
.nav-link {
  flex: 1;
  text-align: center;
  text-decoration: none;
  color: var(--text-dim);
  font-weight: 600;
  font-size: var(--fs-small);
  padding: 0.75rem 0.5rem;
  border-bottom: 2.5px solid transparent;
  transition: color 0.2s, border-color 0.2s;
  position: relative;
}
.nav-link:hover { color: var(--accent); }
.nav-link.active {
  color: var(--accent);
  border-bottom-color: var(--accent);
}

/* --- 4. MAIN CONTENT --- */
.app-main {
  flex: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 1.5rem 1rem 3rem;
  width: 100%;
}
.page {
  display: none;
  width: 100%;
  max-width: 520px;
  margin: 0 auto;
  animation: slideUp 0.35s cubic-bezier(0.22, 1, 0.36, 1);
}
.page.active { display: block; }

@keyframes slideUp {
  from { opacity: 0; transform: translateY(16px); }
  to   { opacity: 1; transform: translateY(0); }
}

/* --- 5. CARDS (Glassmorphism) --- */
.card {
  background: var(--surface);
  backdrop-filter: blur(16px) saturate(1.3);
  -webkit-backdrop-filter: blur(16px) saturate(1.3);
  border-radius: var(--radius);
  padding: 1.75rem;
  border: 1px solid var(--border);
  box-shadow: 0 8px 32px rgba(0,0,0,0.06), 0 0 0 1px var(--border);
  transition: transform 0.3s, box-shadow 0.3s;
}
.card:hover {
  transform: translateY(-2px);
  box-shadow: 0 12px 40px rgba(0,0,0,0.1), 0 0 0 1px var(--border);
}

/* --- 6. FORM ELEMENTS --- */
.input-group {
  margin-bottom: 1.25rem;
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
}
.input-group label {
  font-size: var(--fs-small);
  font-weight: 600;
  color: var(--text-dim);
}
.input-group input {
  padding: 0.85rem 1rem;
  border-radius: var(--radius-sm);
  border: 1.5px solid var(--border);
  background: var(--surface-solid);
  color: var(--text);
  font: inherit;
  font-size: var(--fs-body);
  outline: none;
  width: 100%;
  transition: border-color 0.2s, box-shadow 0.2s;
}
.input-group input:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-surface);
}

/* Primary Button */
.btn-primary {
  width: 100%;
  padding: 0.9rem;
  border-radius: var(--radius-full);
  background: linear-gradient(135deg, var(--accent), var(--accent-light));
  color: var(--accent-on);
  border: none;
  font: inherit;
  font-size: var(--fs-body);
  font-weight: 700;
  cursor: pointer;
  transition: transform 0.15s, box-shadow 0.25s, filter 0.2s;
  box-shadow: 0 4px 16px var(--glow);
  position: relative;
  overflow: hidden;
}
.btn-primary::after {
  content: '';
  position: absolute;
  inset: 0;
  background: linear-gradient(135deg, rgba(255,255,255,0.2), transparent);
  opacity: 0;
  transition: opacity 0.3s;
}
.btn-primary:hover { filter: brightness(1.08); box-shadow: 0 6px 24px var(--glow); }
.btn-primary:hover::after { opacity: 1; }
.btn-primary:active { transform: scale(0.97); }

/* Chips */
.target-section {
  margin-bottom: 1.25rem;
  padding-bottom: 1.25rem;
  border-bottom: 1px solid var(--border);
}
.target-section > label {
  display: block;
  font-size: var(--fs-small);
  font-weight: 600;
  color: var(--text-dim);
  margin-bottom: 0.6rem;
}
.target-chips {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
}
.chip {
  padding: 0.45rem 0.9rem;
  border-radius: var(--radius-full);
  border: 1.5px solid var(--border);
  background: transparent;
  color: var(--text);
  cursor: pointer;
  font-weight: 600;
  font-size: var(--fs-small);
  transition: all 0.2s;
}
.chip:hover { border-color: var(--accent); color: var(--accent); }
.chip.active {
  background: var(--accent);
  color: var(--accent-on);
  border-color: var(--accent);
  box-shadow: 0 2px 8px var(--glow);
}

/* --- 7. RESULTS --- */
.results-container {
  margin-top: 1.25rem;
  padding-top: 1.25rem;
  border-top: 1px solid var(--border);
  animation: slideUp 0.35s cubic-bezier(0.22, 1, 0.36, 1);
}
.current-stat {
  text-align: center;
  margin-bottom: 1.25rem;
}
.stat-label {
  font-size: var(--fs-small);
  color: var(--text-dim);
  text-transform: uppercase;
  letter-spacing: 1.5px;
  font-weight: 600;
}
.current-stat h2 {
  font-size: clamp(2.5rem, 8vw, 3.5rem);
  font-weight: 800;
  background: linear-gradient(135deg, var(--accent), var(--accent-light));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  line-height: 1.1;
}
.actionable-results {
  display: flex;
  flex-direction: column;
  gap: 0.6rem;
}
.result-msg {
  padding: 0.85rem 1rem;
  border-radius: var(--radius-sm);
  background: var(--accent-surface);
  font-weight: 500;
  text-align: center;
  font-size: var(--fs-body);
  border: 1px solid var(--border);
}
.result-msg.success {
  background: var(--success-surface);
  border-color: rgba(16,185,129,0.2);
  color: var(--success);
}
.result-msg.bunkable {
  background: var(--warning-surface);
  border-color: rgba(245,158,11,0.2);
}

/* --- 8. SGPA SPECIFICS --- */
.sem-row {
  display: flex;
  gap: 0.6rem;
  align-items: center;
}
.sem-row input { flex: 1; }
.remove-sem-btn {
  background: var(--accent-surface);
  border-radius: var(--radius-sm);
  transition: all 0.2s;
  flex-shrink: 0;
}
.remove-sem-btn:hover {
  background: var(--danger);
  color: #fff;
  transform: scale(1.1);
}
.add-sem-btn {
  width: 100%;
  margin-bottom: 1.25rem;
  justify-content: center;
  display: flex;
  gap: 0.5rem;
  align-items: center;
}
.cgpa-title {
  font-size: var(--fs-h2);
  font-weight: 700;
  margin-bottom: 1.25rem;
}
#cgpa-results-container .result-msg {
  font-size: var(--fs-h2);
  font-weight: 700;
}

/* --- 9. ABOUT / HERO --- */
.hero-section {
  text-align: center;
  padding: 1.5rem 0;
}
.hero-section .hero-emoji {
  font-size: 3rem;
  display: block;
  margin-bottom: 0.75rem;
  animation: float 3s ease-in-out infinite;
}
@keyframes float {
  0%, 100% { transform: translateY(0); }
  50%      { transform: translateY(-8px); }
}
.hero-section h2 {
  font-size: var(--fs-h2);
  font-weight: 700;
  margin-bottom: 0.5rem;
}
.hero-section p {
  color: var(--text-dim);
  font-size: var(--fs-body);
  line-height: 1.7;
}
.feature-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0.75rem;
  margin-top: 1.25rem;
}
.feature-item {
  background: var(--accent-surface);
  border-radius: var(--radius-sm);
  padding: 1rem;
  text-align: center;
  border: 1px solid var(--border);
  transition: transform 0.2s, box-shadow 0.2s;
}
.feature-item:hover { transform: translateY(-2px); box-shadow: 0 4px 16px rgba(0,0,0,0.06); }
.feature-item .feat-icon { font-size: 1.5rem; margin-bottom: 0.35rem; }
.feature-item .feat-label { font-size: var(--fs-small); font-weight: 600; color: var(--text); }

/* About SEO Content */
.about-seo-content {
  margin-top: 1.5rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--border);
}
.about-seo-content h3 {
  font-size: var(--fs-body);
  font-weight: 700;
  color: var(--text);
  margin-top: 1.25rem;
  margin-bottom: 0.4rem;
}
.about-seo-content h3:first-child {
  margin-top: 0;
}
.about-seo-content p {
  font-size: var(--fs-small);
  color: var(--text-dim);
  line-height: 1.7;
}
.about-seo-content ul {
  list-style: none;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
}
.about-seo-content li {
  font-size: var(--fs-small);
  color: var(--text-dim);
  line-height: 1.6;
  padding-left: 1.2rem;
  position: relative;
}
.about-seo-content li::before {
  content: '✓';
  position: absolute;
  left: 0;
  color: var(--success);
  font-weight: 700;
}
.about-seo-content strong {
  color: var(--text);
  font-weight: 600;
}

/* --- 10. FOOTER --- */
.app-footer {
  text-align: center;
  padding: 1.5rem 1rem;
  font-size: var(--fs-small);
  color: var(--text-dim);
}
.app-footer a {
  color: var(--accent);
  text-decoration: none;
  font-weight: 600;
}
.app-footer a:hover { text-decoration: underline; }

/* --- 11. UTILITIES --- */
.hidden { display: none !important; }

/* Toast notification */
.toast {
  position: fixed;
  bottom: 1.5rem;
  left: 50%;
  transform: translateX(-50%) translateY(80px);
  background: var(--surface-solid);
  color: var(--text);
  padding: 0.75rem 1.5rem;
  border-radius: var(--radius-full);
  box-shadow: 0 8px 32px rgba(0,0,0,0.15);
  border: 1px solid var(--border);
  font-weight: 600;
  font-size: var(--fs-small);
  z-index: 1000;
  opacity: 0;
  transition: transform 0.4s cubic-bezier(0.22, 1, 0.36, 1), opacity 0.4s;
  pointer-events: none;
}
.toast.show {
  transform: translateX(-50%) translateY(0);
  opacity: 1;
}

/* Scrollbar */
::-webkit-scrollbar { width: 6px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb { background: var(--border); border-radius: 3px; }

/* --- 12. AD CONTAINERS --- */
.ad-container {
  width: 100%;
  max-width: 520px;
  margin: 0 auto;
  padding: 0.5rem 1rem;
  text-align: center;
  overflow: hidden;
  min-height: 50px;
}
.ad-container ins {
  display: block;
  border-radius: var(--radius-sm);
  overflow: hidden;
}
.ad-top {
  max-width: 680px;
  padding-top: 0.75rem;
  padding-bottom: 0;
}
.ad-mid {
  margin-top: 0.5rem;
  margin-bottom: 0.5rem;
}
.ad-bottom {
  padding-bottom: 0.75rem;
}

/* --- 13. SEO FAQ SECTION --- */
.seo-faq {
  max-width: 520px;
  margin: 1.5rem auto 0;
  background: var(--surface);
  backdrop-filter: blur(16px) saturate(1.3);
  -webkit-backdrop-filter: blur(16px) saturate(1.3);
  border-radius: var(--radius);
  border: 1px solid var(--border);
  overflow: hidden;
  transition: box-shadow 0.3s;
}
.seo-faq:hover {
  box-shadow: 0 8px 32px rgba(0,0,0,0.06);
}
.seo-faq summary {
  padding: 1rem 1.5rem;
  cursor: pointer;
  list-style: none;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.5rem;
}
.seo-faq summary::-webkit-details-marker { display: none; }
.seo-faq summary::after {
  content: '▸';
  font-size: 1rem;
  color: var(--text-dim);
  transition: transform 0.3s;
}
.seo-faq[open] summary::after {
  transform: rotate(90deg);
}
.seo-faq summary h2 {
  font-size: var(--fs-body);
  font-weight: 700;
  color: var(--text);
  margin: 0;
}
.faq-item {
  padding: 1rem 1.5rem;
  border-top: 1px solid var(--border);
}
.faq-item h3 {
  font-size: var(--fs-body);
  font-weight: 600;
  color: var(--accent);
  margin-bottom: 0.4rem;
}
.faq-item p {
  font-size: var(--fs-small);
  color: var(--text-dim);
  line-height: 1.7;
}

/* --- 14. FOOTER SEO LINKS --- */
.footer-seo {
  margin-top: 0.35rem;
  font-size: 0.75rem;
  color: var(--text-dim);
  opacity: 0.7;
}
.footer-seo a {
  color: var(--accent);
  text-decoration: none;
}
.footer-seo a:hover {
  text-decoration: underline;
}

/* ============================================
   15. RESPONSIVE — TABLET (≤768px)
   ============================================ */
@media (max-width: 768px) {
  .header-content {
    max-width: 100%;
    padding: 0 0.25rem;
  }
  .app-nav {
    max-width: 100%;
  }
  .page {
    max-width: 100%;
  }
  .card {
    padding: 1.5rem 1.25rem;
  }
  .seo-faq {
    max-width: 100%;
  }
  .ad-container {
    max-width: 100%;
  }
  .feature-grid {
    gap: 0.6rem;
  }
}

/* ============================================
   16. RESPONSIVE — SMALL TABLET (≤640px)
   ============================================ */
@media (max-width: 640px) {
  .app-header {
    padding: 1rem 1rem 0;
  }
  .titles h1 {
    font-size: clamp(1.3rem, 5vw, 1.8rem);
  }
  .app-main {
    padding: 1.25rem 0.75rem 2.5rem;
  }
  .card {
    padding: 1.25rem 1rem;
    border-radius: var(--radius-sm);
  }
  .btn-primary {
    padding: 0.8rem;
    font-size: 0.95rem;
  }
  .current-stat h2 {
    font-size: clamp(2rem, 7vw, 2.8rem);
  }
  .seo-faq {
    border-radius: var(--radius-sm);
  }
  .seo-faq summary {
    padding: 0.85rem 1.15rem;
  }
  .faq-item {
    padding: 0.85rem 1.15rem;
  }
}

/* ============================================
   17. RESPONSIVE — MOBILE (≤480px)
   ============================================ */
@media (max-width: 480px) {
  body {
    font-size: 15px;
  }
  .app-header {
    padding: 0.75rem 0.75rem 0;
  }
  .header-content {
    gap: 0.5rem;
  }
  .titles h1 {
    font-size: clamp(1.15rem, 5.5vw, 1.5rem);
  }
  .titles p {
    font-size: 0.75rem;
  }
  .controls select {
    padding: 0.3rem 0.45rem;
    font-size: 0.75rem;
  }
  .icon-btn {
    width: 32px;
    height: 32px;
  }
  .icon-btn svg {
    width: 17px;
    height: 17px;
  }
  .nav-link {
    font-size: 0.72rem;
    padding: 0.6rem 0.3rem;
  }
  .app-main {
    padding: 1rem 0.6rem 2rem;
  }
  .card {
    padding: 1.15rem 0.85rem;
    border-radius: 14px;
    box-shadow: 0 4px 20px rgba(0,0,0,0.05), 0 0 0 1px var(--border);
  }
  .card:hover {
    transform: none;
    box-shadow: 0 4px 20px rgba(0,0,0,0.05), 0 0 0 1px var(--border);
  }
  .target-section > label {
    font-size: 0.78rem;
  }
  .target-chips {
    gap: 0.3rem;
  }
  .chip {
    padding: 0.38rem 0.7rem;
    font-size: 0.75rem;
  }
  .input-group {
    margin-bottom: 1rem;
  }
  .input-group label {
    font-size: 0.78rem;
  }
  .input-group input {
    padding: 0.75rem 0.85rem;
    font-size: 0.95rem;
    border-radius: 10px;
  }
  .btn-primary {
    padding: 0.75rem;
    font-size: 0.9rem;
    border-radius: 50px;
  }
  .current-stat h2 {
    font-size: clamp(1.8rem, 10vw, 2.5rem);
  }
  .stat-label {
    font-size: 0.72rem;
    letter-spacing: 1px;
  }
  .result-msg {
    padding: 0.75rem 0.85rem;
    font-size: 0.88rem;
    border-radius: 10px;
  }
  .cgpa-title {
    font-size: clamp(1.1rem, 4vw, 1.4rem);
    margin-bottom: 1rem;
  }
  .sem-row {
    gap: 0.45rem;
  }
  .add-sem-btn {
    margin-bottom: 1rem;
    font-size: 0.78rem;
  }
  .hero-section {
    padding: 1rem 0;
  }
  .hero-section .hero-emoji {
    font-size: 2.2rem;
  }
  .hero-section h2 {
    font-size: clamp(1.1rem, 4vw, 1.4rem);
  }
  .hero-section p {
    font-size: 0.88rem;
  }
  .feature-grid {
    grid-template-columns: 1fr 1fr;
    gap: 0.5rem;
  }
  .feature-item {
    padding: 0.75rem 0.5rem;
    border-radius: 10px;
  }
  .feature-item .feat-icon {
    font-size: 1.25rem;
  }
  .feature-item .feat-label {
    font-size: 0.72rem;
  }
  .app-footer {
    padding: 1.25rem 0.75rem;
    font-size: 0.72rem;
  }
  .footer-seo {
    font-size: 0.65rem;
  }
  .seo-faq {
    border-radius: 14px;
    margin-top: 1rem;
  }
  .seo-faq summary {
    padding: 0.75rem 1rem;
  }
  .seo-faq summary h2 {
    font-size: 0.88rem;
  }
  .faq-item {
    padding: 0.75rem 1rem;
  }
  .faq-item h3 {
    font-size: 0.88rem;
  }
  .faq-item p {
    font-size: 0.75rem;
  }
  .ad-container {
    padding: 0.35rem 0.6rem;
    min-height: 40px;
  }
  .toast {
    font-size: 0.75rem;
    padding: 0.6rem 1.2rem;
    bottom: 1rem;
  }
}

/* ============================================
   18. RESPONSIVE — VERY SMALL (≤360px)
   ============================================ */
@media (max-width: 360px) {
  .titles h1 {
    font-size: 1.1rem;
  }
  .nav-link {
    font-size: 0.65rem;
    padding: 0.55rem 0.2rem;
  }
  .chip {
    padding: 0.32rem 0.55rem;
    font-size: 0.7rem;
  }
  .card {
    padding: 1rem 0.75rem;
  }
  .feature-grid {
    grid-template-columns: 1fr;
  }
}