/* =============================================
   PhysicsLab – Styles
   ============================================= */

/* --- Reset & Base --- */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

:root {
  --navy:       #0F1B2D;
  --navy-mid:   #1A2B44;
  --navy-light: #253A5A;
  --blue:       #1A9FE0;
  --blue-light: #4DB8F0;
  --red:        #E05252;
  --red-dark:   #C0392B;
  --green:      #27AE60;
  --gold:       #F39C12;
  --white:      #FFFFFF;
  --off-white:  #F0F4F8;
  --grey:       #8899AA;
  --text-dim:   #A0B0C0;
  --card-bg:    #FFFFFF;
  --shadow:     0 4px 24px rgba(0,0,0,0.10);
  --radius:     12px;
  --transition: 0.25s ease;
}

html { scroll-behavior: smooth; font-size: 16px; }

body {
  font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;
  background: var(--off-white);
  color: var(--navy);
  line-height: 1.6;
}

/* =============================================
   NAVBAR  (Section ①)
   ============================================= */
#navbar {
  position: fixed;
  top: 0; left: 0; right: 0;
  z-index: 1000;
  background: var(--navy);
  height: 64px;
  display: flex;
  align-items: center;
  padding: 0 5%;
  box-shadow: 0 2px 16px rgba(0,0,0,0.35);
}

.nav-logo {
  display: flex;
  align-items: center;
  gap: 10px;
  text-decoration: none;
  flex-shrink: 0;
}

.nav-logo svg { width: 36px; height: 36px; }

.nav-logo span {
  font-size: 1.35rem;
  font-weight: 700;
  color: var(--white);
  letter-spacing: -0.5px;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 36px;
  margin-left: auto;
  list-style: none;
}

.nav-links a {
  color: var(--white);
  text-decoration: none;
  font-size: 0.95rem;
  opacity: 0.85;
  transition: opacity var(--transition);
}
.nav-links a:hover { opacity: 1; }

.nav-badge {
  background: var(--red);
  color: var(--white);
  font-size: 0.82rem;
  font-weight: 700;
  padding: 5px 14px;
  border-radius: 6px;
  letter-spacing: 0.5px;
  text-decoration: none;
  white-space: nowrap;
}

.hamburger {
  display: none;
  flex-direction: column;
  gap: 5px;
  cursor: pointer;
  margin-left: auto;
  background: none;
  border: none;
  padding: 4px;
}
.hamburger span {
  display: block;
  width: 24px; height: 2px;
  background: var(--white);
  border-radius: 2px;
  transition: var(--transition);
}

/* =============================================
   HERO  (Section ②)
   ============================================= */
#home {
  min-height: 100vh;
  background: var(--navy);
  display: flex;
  flex-direction: column;
  justify-content: center;
  padding: 100px 5% 60px;
  position: relative;
  overflow: hidden;
}

.hero-inner {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 40px;
  align-items: center;
  max-width: 1100px;
  margin: 0 auto;
  width: 100%;
}

.hero-text h1 {
  font-size: clamp(2.4rem, 5vw, 3.6rem);
  font-weight: 800;
  color: var(--white);
  line-height: 1.15;
  margin-bottom: 18px;
}

.hero-text p {
  font-size: 1.15rem;
  color: var(--text-dim);
  max-width: 480px;
  margin-bottom: 36px;
}

.hero-ctas {
  display: flex;
  gap: 16px;
  flex-wrap: wrap;
}

.btn-primary {
  background: var(--red);
  color: var(--white);
  border: none;
  padding: 14px 30px;
  border-radius: 8px;
  font-size: 1rem;
  font-weight: 700;
  cursor: pointer;
  text-decoration: none;
  transition: background var(--transition), transform var(--transition);
  display: inline-block;
}
.btn-primary:hover { background: var(--red-dark); transform: translateY(-2px); }

.btn-secondary {
  background: transparent;
  color: var(--white);
  border: 2px solid rgba(255,255,255,0.5);
  padding: 14px 30px;
  border-radius: 8px;
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  text-decoration: none;
  transition: border-color var(--transition), transform var(--transition);
  display: inline-block;
}
.btn-secondary:hover { border-color: var(--white); transform: translateY(-2px); }

/* Rocket illustration */
.hero-visual {
  position: relative;
  width: 220px;
  height: 220px;
}

.hero-circle-bg {
  position: absolute;
  inset: 0;
  border-radius: 50%;
  background: var(--navy-light);
  opacity: 0.6;
}

.hero-circle-sm {
  position: absolute;
  width: 140px; height: 140px;
  bottom: -20px; right: -20px;
  border-radius: 50%;
  background: var(--navy-mid);
  opacity: 0.5;
}

.hero-rocket {
  position: absolute;
  top: 50%; left: 50%;
  transform: translate(-50%, -55%) rotate(-30deg);
  font-size: 90px;
  animation: float 3s ease-in-out infinite;
}

@keyframes float {
  0%, 100% { transform: translate(-50%, -55%) rotate(-30deg); }
  50% { transform: translate(-50%, -65%) rotate(-30deg); }
}

/* Stats bar */
.stats-bar {
  display: flex;
  gap: 0;
  margin-top: 56px;
  max-width: 1100px;
  margin-left: auto;
  margin-right: auto;
  width: 100%;
  border-top: 1px solid rgba(255,255,255,0.08);
  padding-top: 36px;
  flex-wrap: wrap;
}

.stat-item {
  display: flex;
  align-items: center;
  gap: 12px;
  flex: 1;
  min-width: 160px;
}

.stat-icon { font-size: 1.8rem; }

.stat-text strong {
  display: block;
  font-size: 1.5rem;
  font-weight: 800;
  color: var(--white);
}

.stat-text span {
  font-size: 0.85rem;
  color: var(--text-dim);
}

/* =============================================
   MODULE CARDS  (Section ③)
   ============================================= */
#modules {
  padding: 90px 5%;
  background: var(--off-white);
}

.section-header {
  text-align: center;
  margin-bottom: 52px;
}
.section-header h2 {
  font-size: 2rem;
  font-weight: 800;
  color: var(--navy);
  margin-bottom: 8px;
}
.section-header p {
  color: var(--grey);
  font-size: 1rem;
}

.module-cards-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 28px;
  max-width: 1100px;
  margin: 0 auto;
}

.module-card {
  background: var(--card-bg);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  overflow: hidden;
  transition: transform var(--transition), box-shadow var(--transition);
  border-top: 4px solid transparent;
}
.module-card:hover { transform: translateY(-6px); box-shadow: 0 12px 40px rgba(0,0,0,0.15); }
.module-card.kinematics { border-top-color: var(--blue); }
.module-card.projectile  { border-top-color: var(--red); }
.module-card.angular     { border-top-color: var(--green); }

.card-header {
  display: flex;
  align-items: center;
  gap: 14px;
  padding: 24px 24px 16px;
}

.card-icon {
  width: 50px; height: 50px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.4rem;
  flex-shrink: 0;
}
.kinematics .card-icon { background: #EBF6FE; }
.projectile  .card-icon { background: #FEF0EE; }
.angular     .card-icon { background: #EAF7EF; }

.card-header-text .module-label {
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 1.5px;
  text-transform: uppercase;
  margin-bottom: 2px;
}
.kinematics .module-label { color: var(--blue); }
.projectile  .module-label { color: var(--red); }
.angular     .module-label { color: var(--green); }

.card-header-text h3 {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--navy);
}

.card-preview {
  margin: 0 24px;
  border-radius: 8px;
  overflow: hidden;
  background: #F7FAFC;
  border: 1px solid #E0E8EF;
  height: 160px;
  position: relative;
}

.card-preview canvas { width: 100%; height: 100%; }

.card-body {
  padding: 16px 24px;
  color: var(--grey);
  font-size: 0.92rem;
  line-height: 1.6;
}

.card-footer { padding: 16px 24px 24px; }

.btn-module {
  display: inline-block;
  padding: 11px 24px;
  border-radius: 7px;
  font-size: 0.95rem;
  font-weight: 700;
  text-decoration: none;
  border: none;
  cursor: pointer;
  transition: filter var(--transition), transform var(--transition);
  color: var(--white);
  width: 100%;
  text-align: center;
}
.btn-module:hover { filter: brightness(1.1); transform: translateY(-1px); }
.kinematics .btn-module { background: var(--blue); }
.projectile  .btn-module { background: var(--red); }
.angular     .btn-module { background: var(--green); }

/* =============================================
   MODULE DETAIL SECTIONS  (Sections ④ ⑤)
   ============================================= */
.module-detail {
  padding: 90px 5%;
}
.module-detail.kinematics-section { background: #F0F8FF; }
.module-detail.projectile-section { background: #FFF5F5; }

.detail-inner {
  max-width: 1100px;
  margin: 0 auto;
}

.detail-header {
  display: flex;
  align-items: center;
  gap: 16px;
  margin-bottom: 36px;
}

.detail-badge {
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 2px;
  text-transform: uppercase;
  padding: 4px 12px;
  border-radius: 20px;
  color: var(--white);
}
.kinematics-section .detail-badge { background: var(--blue); }
.projectile-section  .detail-badge { background: var(--red); }

.detail-header h2 {
  font-size: 1.75rem;
  font-weight: 800;
  color: var(--navy);
}

.sim-layout {
  display: grid;
  grid-template-columns: 1fr 340px;
  gap: 28px;
  align-items: start;
}

.sim-canvas-wrap {
  background: var(--white);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  overflow: hidden;
  padding: 20px;
}

.sim-canvas-wrap canvas {
  width: 100%;
  border-radius: 8px;
  display: block;
}

.sim-controls {
  background: var(--white);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 24px;
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.sim-controls h4 {
  font-size: 0.8rem;
  font-weight: 700;
  letter-spacing: 1.5px;
  text-transform: uppercase;
  color: var(--grey);
  margin-bottom: -8px;
}

.control-group { display: flex; flex-direction: column; gap: 8px; }

.control-group label {
  font-size: 0.88rem;
  font-weight: 600;
  color: var(--navy);
  display: flex;
  justify-content: space-between;
}

.control-group label span {
  font-weight: 700;
  color: var(--blue);
}
.projectile-section .control-group label span { color: var(--red); }

input[type="range"] {
  -webkit-appearance: none;
  width: 100%;
  height: 6px;
  border-radius: 3px;
  background: #DDE6EF;
  outline: none;
  cursor: pointer;
}
input[type="range"]::-webkit-slider-thumb {
  -webkit-appearance: none;
  width: 18px; height: 18px;
  border-radius: 50%;
  background: var(--blue);
  box-shadow: 0 2px 6px rgba(26,159,224,0.35);
  transition: transform var(--transition);
}
input[type="range"]::-webkit-slider-thumb:hover { transform: scale(1.2); }
.projectile-section input[type="range"]::-webkit-slider-thumb { background: var(--red); }

.info-cards {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 10px;
}

.info-card {
  background: var(--off-white);
  border-radius: 8px;
  padding: 10px 12px;
  text-align: center;
}

.info-card .ic-label {
  font-size: 0.72rem;
  color: var(--grey);
  text-transform: uppercase;
  letter-spacing: 0.8px;
  margin-bottom: 2px;
}

.info-card .ic-value {
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--navy);
}

.btn-sim {
  padding: 12px;
  border-radius: 8px;
  border: none;
  font-size: 0.95rem;
  font-weight: 700;
  cursor: pointer;
  transition: filter var(--transition), transform var(--transition);
  color: var(--white);
}
.btn-sim:hover { filter: brightness(1.1); transform: translateY(-1px); }
.btn-sim.blue-btn { background: var(--blue); }
.btn-sim.red-btn  { background: var(--red); }
.btn-sim.outline  {
  background: transparent;
  border: 2px solid currentColor;
  color: var(--grey);
}
.btn-sim.outline:hover { color: var(--navy); border-color: var(--navy); filter: none; }

.btn-row { display: flex; gap: 10px; }
.btn-row .btn-sim { flex: 1; }

/* Concept cards */
.concept-box {
  margin-top: 28px;
  background: var(--white);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 24px;
}

.concept-box h4 {
  font-size: 0.8rem;
  font-weight: 700;
  letter-spacing: 1.5px;
  text-transform: uppercase;
  color: var(--grey);
  margin-bottom: 16px;
}

.concept-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}

.concept-tag {
  background: var(--off-white);
  border-radius: 20px;
  padding: 6px 14px;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--navy-mid);
  border: 1px solid #DDE6EF;
}

/* Quiz inline */
.quiz-box {
  margin-top: 20px;
  background: var(--white);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 24px;
}
.quiz-box h4 {
  font-size: 0.85rem;
  font-weight: 700;
  letter-spacing: 1px;
  text-transform: uppercase;
  color: var(--grey);
  margin-bottom: 12px;
}
.quiz-question { font-size: 0.95rem; font-weight: 600; color: var(--navy); margin-bottom: 14px; }
.quiz-options { display: flex; flex-direction: column; gap: 8px; }
.quiz-option {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 10px 14px;
  border-radius: 8px;
  border: 2px solid #DDE6EF;
  cursor: pointer;
  font-size: 0.9rem;
  transition: var(--transition);
  background: var(--white);
}
.quiz-option:hover { border-color: var(--blue); background: #EBF6FE; }
.quiz-option.correct { border-color: var(--green); background: #EAF7EF; color: var(--green); }
.quiz-option.wrong   { border-color: var(--red);   background: #FEF0EE; color: var(--red); }
.quiz-feedback { margin-top: 10px; font-size: 0.88rem; font-weight: 600; min-height: 20px; }

/* =============================================
   FOOTER  (Section ⑥)
   ============================================= */
#footer-cta {
  background: #2B4270;
  padding: 70px 5%;
  text-align: center;
}

#footer-cta .cta-icon { font-size: 3rem; margin-bottom: 16px; display: block; }

#footer-cta h2 {
  font-size: 2rem;
  font-weight: 800;
  color: var(--white);
  margin-bottom: 10px;
}

#footer-cta p {
  color: rgba(255,255,255,0.7);
  margin-bottom: 28px;
  font-size: 1rem;
}

footer {
  background: var(--navy);
  padding: 48px 5% 28px;
}

.footer-grid {
  display: grid;
  grid-template-columns: 1.5fr 1fr 1fr 1fr;
  gap: 40px;
  max-width: 1100px;
  margin: 0 auto 36px;
}

.footer-brand .brand-name {
  display: flex;
  align-items: center;
  gap: 10px;
  color: var(--white);
  font-size: 1.2rem;
  font-weight: 700;
  margin-bottom: 12px;
  text-decoration: none;
}

.footer-brand p {
  color: var(--text-dim);
  font-size: 0.88rem;
  line-height: 1.65;
}

.footer-col h5 {
  color: var(--white);
  font-size: 0.9rem;
  font-weight: 700;
  margin-bottom: 16px;
  letter-spacing: 0.5px;
}

.footer-col ul { list-style: none; display: flex; flex-direction: column; gap: 10px; }

.footer-col ul li a {
  color: var(--text-dim);
  text-decoration: none;
  font-size: 0.88rem;
  transition: color var(--transition);
}
.footer-col ul li a:hover { color: var(--white); }

.footer-contact-list li {
  display: flex;
  align-items: center;
  gap: 8px;
}

.contact-icon {
  font-size: 0.9rem;
  flex-shrink: 0;
  opacity: 0.75;
}

.footer-bottom {
  border-top: 1px solid rgba(255,255,255,0.08);
  padding-top: 20px;
  text-align: center;
  color: var(--text-dim);
  font-size: 0.82rem;
  max-width: 1100px;
  margin: 0 auto;
}

/* =============================================
   RESPONSIVE
   ============================================= */
@media (max-width: 900px) {
  .module-cards-grid { grid-template-columns: 1fr 1fr; }
  .sim-layout { grid-template-columns: 1fr; }
  .footer-grid { grid-template-columns: 1fr 1fr; }
  .hero-visual { display: none; }
}

@media (max-width: 640px) {
  .nav-links { display: none; }
  .hamburger { display: flex; }
  .nav-links.open {
    display: flex;
    flex-direction: column;
    position: fixed;
    top: 64px; left: 0; right: 0;
    background: var(--navy-mid);
    padding: 20px 5%;
    gap: 20px;
    box-shadow: 0 8px 20px rgba(0,0,0,0.3);
  }
  .nav-links.open li { list-style: none; }
  .module-cards-grid { grid-template-columns: 1fr; }
  .footer-grid { grid-template-columns: 1fr; gap: 28px; }
  .stats-bar { gap: 24px; }
  .info-cards { grid-template-columns: 1fr 1fr; }
}