/*
 * QueStudy Landing Page — Premium SaaS Design System
 * Apple × Stripe × Notion × Linear × EdTech
 * Version: 5.0
 */

/* ==========================================================================
   1. DESIGN TOKENS
   ========================================================================== */
:root {
  /* Colors */
  --qs-blue: #2563EB;
  --qs-blue-dark: #1D4ED8;
  --qs-blue-light: #3B82F6;
  --qs-blue-50: #EFF6FF;
  --qs-blue-100: #DBEAFE;
  --qs-blue-border: #EEF2FF;
  --qs-navy: #0F172A;
  --qs-navy-2: #1E293B;
  --qs-navy-3: #334155;
  --qs-white: #FFFFFF;
  --qs-bg: #F8FAFC;
  --qs-surface: #FFFFFF;
  --qs-heading: #0F172A;
  --qs-body: #64748B;
  --qs-body-dark: #334155;
  --qs-muted: #94A3B8;
  --qs-border: #E5E7EB;
  --qs-border-light: #F1F5F9;

  /* Spacing */
  --qs-section: 120px;
  --qs-gap: 20px;
  --qs-container: 1280px;

  /* Radius */
  --qs-r: 20px;
  --qs-r-lg: 24px;
  --qs-r-md: 16px;
  --qs-r-sm: 12px;
  --qs-r-xs: 8px;
  --qs-r-full: 9999px;

  /* Shadows */
  --qs-sh-1: 0 1px 3px rgba(0,0,0,.05), 0 1px 2px rgba(0,0,0,.03);
  --qs-sh-2: 0 4px 12px rgba(0,0,0,.05), 0 1px 3px rgba(0,0,0,.03);
  --qs-sh-3: 0 10px 30px rgba(0,0,0,.06), 0 2px 8px rgba(0,0,0,.03);
  --qs-sh-4: 0 20px 50px rgba(0,0,0,.08), 0 4px 16px rgba(0,0,0,.03);
  --qs-sh-blue: 0 4px 16px rgba(37,99,235,.25);

  /* Motion */
  --qs-ease: cubic-bezier(.4,0,.2,1);
  --qs-spring: cubic-bezier(.32,.72,0,1);

  /* Typography */
  --qs-font: 'Inter',-apple-system,BlinkMacSystemFont,'Segoe UI',Roboto,system-ui,sans-serif;
}

/* ==========================================================================
   2. RESET & BASE
   ========================================================================== */
*,*::before,*::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
body.qs {
  font-family: var(--qs-font);
  background: var(--qs-white);
  color: var(--qs-heading);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  overflow-x: hidden;
}
img { max-width: 100%; display: block; }
a { color: inherit; text-decoration: none; }
button { font: inherit; border: none; background: none; cursor: pointer; color: inherit; }
input, select { font: inherit; }
::selection { background: var(--qs-blue); color: #fff; }

/* ==========================================================================
   3. UTILITIES
   ========================================================================== */
.qs-container { max-width: var(--qs-container); margin: 0 auto; padding: 0 24px; }
.qs-section-pad { padding: var(--qs-section) 0; }
.qs-text-blue { color: var(--qs-blue); }
.qs-heading { font-size: clamp(28px,3.5vw,42px); font-weight: 800; letter-spacing: -.03em; text-align: center; line-height: 1.15; margin-bottom: 16px; }
.qs-subheading { font-size: 17px; color: var(--qs-body); text-align: center; max-width: 560px; margin: 0 auto 56px; line-height: 1.65; }

/* ==========================================================================
   4. SCROLL REVEAL — Progressive Enhancement
      Content visible by default (no-js).
      JS adds body.qs-js → hides .qs-r → IntersectionObserver reveals.
   ========================================================================== */
body.qs-js .qs-r {
  opacity: 0;
  transform: translateY(24px);
  transition: opacity .6s var(--qs-ease), transform .6s var(--qs-spring);
}
body.qs-js .qs-r.qs-rv {
  opacity: 1;
  transform: none;
}

/* ==========================================================================
   5. HEADER
   ========================================================================== */
.qs-header {
  position: fixed;
  top: 0; left: 0; right: 0;
  z-index: 1000;
  background: var(--qs-white);
  transition: box-shadow .3s var(--qs-ease), transform .3s var(--qs-ease), backdrop-filter .3s var(--qs-ease), background .3s var(--qs-ease);
}
.qs-header.scrolled {
  box-shadow: 0 1px 0 rgba(0,0,0,.06);
  background: rgba(255,255,255,.85);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
}
.qs-header.hide-up { transform: translateY(-100%); }
.qs-header-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 80px;
}

/* Logo */
.qs-logo {
  display: flex;
  align-items: center;
  gap: 10px;
  flex-shrink: 0;
}
.qs-logo-icon {
  transition: transform .3s var(--qs-spring);
}
.qs-logo:hover .qs-logo-icon { transform: rotate(-6deg) scale(1.05); }
.qs-logo-meta { display: flex; flex-direction: column; }
.qs-logo-name { font-size: 18px; font-weight: 800; letter-spacing: -.02em; line-height: 1.2; color: var(--qs-heading); }
.qs-logo-tagline { font-size: 11px; color: var(--qs-muted); font-weight: 500; line-height: 1.2; }

/* Desktop nav */
.qs-desktop-nav {
  display: flex;
  align-items: center;
  gap: 2px;
}
.qs-nav-link {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  padding: 8px 14px;
  font-size: 14px;
  font-weight: 500;
  color: var(--qs-body-dark);
  border-radius: var(--qs-r-xs);
  transition: all .2s var(--qs-ease);
  white-space: nowrap;
  background: none;
  border: none;
}
.qs-nav-link:hover,
.qs-nav-link.active {
  color: var(--qs-heading);
  background: var(--qs-bg);
}
.qs-nav-link svg {
  transition: transform .2s;
  flex-shrink: 0;
}

/* Dropdown */
.qs-dropdown-wrap { position: relative; }
.qs-dropdown {
  position: absolute;
  top: calc(100% + 8px);
  left: 50%;
  transform: translateX(-50%) translateY(8px);
  opacity: 0;
  visibility: hidden;
  pointer-events: none;
  background: var(--qs-surface);
  border: 1px solid var(--qs-border);
  border-radius: var(--qs-r-md);
  padding: 8px;
  min-width: 240px;
  box-shadow: var(--qs-sh-3);
  transition: all .25s var(--qs-ease);
  z-index: 200;
}
.qs-dropdown-wrap.open .qs-dropdown {
  opacity: 1;
  visibility: visible;
  pointer-events: auto;
  transform: translateX(-50%) translateY(0);
}
.qs-dropdown-wrap.open .qs-nav-link svg {
  transform: rotate(180deg);
}
.qs-dd-item {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 10px 14px;
  border-radius: var(--qs-r-xs);
  font-size: 14px;
  font-weight: 500;
  color: var(--qs-body-dark);
  transition: all .15s;
  white-space: nowrap;
}
.qs-dd-item:hover {
  background: var(--qs-blue-50);
  color: var(--qs-blue);
}
.qs-dd-icon {
  font-size: 16px;
  width: 24px;
  text-align: center;
  flex-shrink: 0;
}

/* Header actions */
.qs-actions {
  display: flex;
  align-items: center;
  gap: 6px;
}
.qs-icon-btn {
  width: 38px;
  height: 38px;
  border-radius: var(--qs-r-xs);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--qs-muted);
  transition: all .2s;
}
.qs-icon-btn:hover {
  background: var(--qs-bg);
  color: var(--qs-heading);
}
.qs-btn-login {
  padding: 8px 16px;
  font-size: 14px;
  font-weight: 600;
  color: var(--qs-body-dark);
  border-radius: var(--qs-r-xs);
  transition: all .2s;
}
.qs-btn-login:hover {
  color: var(--qs-blue);
  background: var(--qs-blue-50);
}
.qs-btn-cta-sm {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 10px 20px;
  font-size: 14px;
  font-weight: 600;
  color: #fff;
  background: var(--qs-blue);
  border-radius: var(--qs-r-sm);
  transition: all .3s var(--qs-ease);
  box-shadow: var(--qs-sh-blue);
}
.qs-btn-cta-sm:hover {
  background: var(--qs-blue-dark);
  transform: translateY(-1px);
  box-shadow: 0 6px 20px rgba(37,99,235,.35);
}

/* Dark mode toggle */
.qs-dark-toggle .qs-moon { display: none; }
body.qs-dark .qs-dark-toggle .qs-sun { display: none; }
body.qs-dark .qs-dark-toggle .qs-moon { display: block; }

/* Hamburger */
.qs-hamburger {
  display: none;
  width: 40px;
  height: 40px;
  border-radius: var(--qs-r-xs);
  align-items: center;
  justify-content: center;
  flex-direction: column;
  gap: 5px;
  z-index: 1001;
  transition: background .2s;
}
.qs-hamburger:hover { background: var(--qs-bg); }
.qs-hamburger span {
  display: block;
  width: 20px;
  height: 2px;
  background: var(--qs-heading);
  border-radius: 2px;
  transition: all .3s var(--qs-spring);
}
.qs-hamburger.on span:nth-child(1) { transform: translateY(7px) rotate(45deg); }
.qs-hamburger.on span:nth-child(2) { opacity: 0; transform: scaleX(0); }
.qs-hamburger.on span:nth-child(3) { transform: translateY(-7px) rotate(-45deg); }

/* Mobile menu */
.qs-mobile {
  display: none;
  position: fixed;
  top: 80px; left: 0; right: 0; bottom: 0;
  background: rgba(248,250,252,.97);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  z-index: 998;
  overflow-y: auto;
}
.qs-mobile.open { display: block; }
.qs-mobile-inner {
  padding: 24px;
  display: flex;
  flex-direction: column;
  gap: 4px;
}
.qs-m-link {
  padding: 14px 16px;
  font-size: 16px;
  font-weight: 500;
  color: var(--qs-heading);
  border-radius: var(--qs-r-sm);
  transition: background .2s;
}
.qs-m-link:hover { background: var(--qs-bg); }
.qs-m-actions {
  margin-top: 24px;
  display: flex;
  flex-direction: column;
  gap: 12px;
}
.qs-m-btn-out {
  padding: 14px;
  text-align: center;
  font-weight: 600;
  border: 1.5px solid var(--qs-border);
  border-radius: var(--qs-r-sm);
  transition: all .2s;
  color: var(--qs-heading);
}
.qs-m-btn-out:hover { border-color: var(--qs-blue); color: var(--qs-blue); }
.qs-m-btn-fill {
  padding: 14px;
  text-align: center;
  font-weight: 600;
  color: #fff;
  background: var(--qs-blue);
  border-radius: var(--qs-r-sm);
  box-shadow: var(--qs-sh-blue);
  transition: all .3s;
}
.qs-m-btn-fill:hover { background: var(--qs-blue-dark); }

/* ==========================================================================
   6. HERO
   ========================================================================== */
.qs-hero {
  padding: 160px 0 var(--qs-section);
  min-height: 100vh;
  display: flex;
  align-items: center;
}
.qs-hero-grid {
  display: grid;
  grid-template-columns: 45fr 55fr;
  gap: 60px;
  align-items: center;
}
.qs-hero-left { max-width: 560px; }

/* Badge */
.qs-badge {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  background: var(--qs-blue-50);
  color: var(--qs-blue);
  font-size: 12px;
  font-weight: 700;
  padding: 8px 18px;
  border-radius: var(--qs-r-full);
  border: 1px solid var(--qs-blue-100);
  margin-bottom: 28px;
  letter-spacing: .06em;
  text-transform: uppercase;
}
.qs-badge-dot {
  width: 7px;
  height: 7px;
  border-radius: 50%;
  background: var(--qs-blue);
  animation: qs-pulse 2s ease-in-out infinite;
}
@keyframes qs-pulse {
  0%,100% { opacity: 1; transform: scale(1); }
  50% { opacity: .4; transform: scale(1.5); }
}

/* Title */
.qs-hero-title {
  font-size: 64px;
  font-weight: 800;
  line-height: 1.05;
  letter-spacing: -.04em;
  margin-bottom: 24px;
}
.qs-hero-desc {
  font-size: 18px;
  color: var(--qs-body);
  line-height: 1.7;
  margin-bottom: 36px;
}

/* Buttons */
.qs-hero-btns {
  display: flex;
  gap: 14px;
  flex-wrap: wrap;
  margin-bottom: 32px;
}
.qs-btn-hero {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 16px 32px;
  font-size: 16px;
  font-weight: 700;
  color: #fff;
  background: var(--qs-blue);
  border-radius: var(--qs-r-sm);
  transition: all .3s var(--qs-ease);
  box-shadow: 0 4px 16px rgba(37,99,235,.3);
}
.qs-btn-hero:hover {
  background: var(--qs-blue-dark);
  transform: translateY(-2px);
  box-shadow: 0 8px 28px rgba(37,99,235,.4);
}
.qs-btn-hero svg { transition: transform .3s var(--qs-spring); }
.qs-btn-hero:hover svg { transform: translateX(3px); }
.qs-btn-hero-outline {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 16px 28px;
  font-size: 16px;
  font-weight: 600;
  color: var(--qs-heading);
  border: 1.5px solid var(--qs-border);
  border-radius: var(--qs-r-sm);
  transition: all .3s;
  background: transparent;
}
.qs-btn-hero-outline:hover {
  border-color: var(--qs-blue);
  color: var(--qs-blue);
  background: var(--qs-blue-50);
  transform: translateY(-2px);
}

/* Feature checks */
.qs-checks {
  display: flex;
  flex-wrap: wrap;
  gap: 16px;
  margin-bottom: 32px;
}
.qs-check {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 13px;
  font-weight: 500;
  color: var(--qs-body);
}
.qs-check svg { flex-shrink: 0; }

/* Social proof */
.qs-social {
  display: flex;
  align-items: center;
  gap: 14px;
}
.qs-avatars { display: flex; }
.qs-av {
  width: 34px;
  height: 34px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  color: #fff;
  font-size: 12px;
  font-weight: 700;
  border: 2.5px solid var(--qs-white);
  margin-right: -10px;
  transition: transform .3s var(--qs-spring);
}
.qs-av:last-child { margin-right: 0; }
.qs-av:hover { transform: translateY(-3px) scale(1.15); z-index: 1; }
.qs-social-text {
  font-size: 14px;
  color: var(--qs-body);
  line-height: 1.4;
}
.qs-social-text strong {
  color: var(--qs-heading);
  font-weight: 700;
}

/* ==========================================================================
   7. HERO ILLUSTRATION
   ========================================================================== */
.qs-hero-right {
  position: relative;
  display: flex;
  align-items: center;
  justify-content: center;
}
.qs-illust {
  position: relative;
  width: 100%;
  max-width: 560px;
  aspect-ratio: 6/5;
}

/* Laptop */
.qs-laptop {
  position: absolute;
  left: 50%;
  top: 50%;
  transform: translate(-50%, -48%);
  width: 280px;
  z-index: 5;
}
.qs-laptop-screen {
  background: linear-gradient(135deg, #0F172A, #1E293B);
  border-radius: 12px 12px 0 0;
  overflow: hidden;
  border: 2px solid #334155;
  box-shadow: 0 0 40px rgba(37,99,235,.15);
}
.qs-screen-bar {
  background: #1a2332;
  padding: 8px 12px;
  display: flex;
  align-items: center;
  gap: 8px;
  border-bottom: 1px solid rgba(255,255,255,.06);
}
.qs-bar-dots { display: flex; gap: 4px; }
.qs-bar-dots span { width: 7px; height: 7px; border-radius: 50%; background: rgba(255,255,255,.12); }
.qs-bar-dots span:nth-child(1) { background: #EF4444; }
.qs-bar-dots span:nth-child(2) { background: #F59E0B; }
.qs-bar-dots span:nth-child(3) { background: #10B981; }
.qs-bar-title { font-size: 10px; color: rgba(255,255,255,.5); font-weight: 500; margin-left: auto; }
.qs-screen-body {
  padding: 14px 12px;
  display: flex;
  flex-direction: column;
  gap: 10px;
  min-height: 140px;
}
.qs-chat-row { display: flex; gap: 6px; align-items: flex-start; }
.qs-chat-row.user { justify-content: flex-end; }
.qs-chat-av {
  width: 22px;
  height: 22px;
  border-radius: 6px;
  background: var(--qs-blue);
  display: flex;
  align-items: center;
  justify-content: center;
  color: #fff;
  font-size: 8px;
  font-weight: 700;
  flex-shrink: 0;
}
.qs-chat-bub {
  font-size: 10px;
  line-height: 1.4;
  padding: 7px 10px;
  border-radius: 8px;
  max-width: 190px;
  background: rgba(255,255,255,.08);
  color: rgba(255,255,255,.8);
}
.qs-chat-bub.user-bub { background: var(--qs-blue); color: #fff; }
.qs-typing { display: flex; gap: 4px; padding: 0 4px; }
.qs-typing span {
  width: 5px; height: 5px; border-radius: 50%;
  background: rgba(255,255,255,.3);
  animation: qs-type 1.4s ease-in-out infinite;
}
.qs-typing span:nth-child(2) { animation-delay: .2s; }
.qs-typing span:nth-child(3) { animation-delay: .4s; }
@keyframes qs-type {
  0%,60%,100% { opacity: .3; transform: translateY(0); }
  30% { opacity: 1; transform: translateY(-4px); }
}
.qs-laptop-base {
  height: 10px;
  background: linear-gradient(180deg, #334155, #475569);
  border-radius: 0 0 8px 8px;
}

/* Floating cards */
.qs-fcard {
  position: absolute;
  display: flex;
  align-items: center;
  gap: 8px;
  background: var(--qs-surface);
  border: 1px solid var(--qs-border);
  border-radius: var(--qs-r-sm);
  padding: 8px 14px;
  font-size: 11px;
  font-weight: 600;
  color: var(--qs-heading);
  box-shadow: var(--qs-sh-2);
  z-index: 6;
  white-space: nowrap;
  animation: qs-float 6s ease-in-out infinite;
}
.qs-fcard-icon { font-size: 14px; }
.qs-fc1 { top: 4%; left: 0; }
.qs-fc2 { top: 4%; right: 0; animation-delay: .8s; }
.qs-fc3 { top: 38%; left: -6%; animation-delay: 1.6s; }
.qs-fc4 { top: 38%; right: -6%; animation-delay: 2.4s; }
.qs-fc5 { bottom: 10%; left: 0; animation-delay: 3.2s; }
.qs-fc6 { bottom: 10%; right: 0; animation-delay: 4s; }
@keyframes qs-float {
  0%,100% { transform: translateY(0); }
  50% { transform: translateY(-8px); }
}

/* Illustration decorations */
.qs-illust-lines {
  position: absolute;
  top: 0;
  right: 0;
  bottom: 0;
  left: 0;
  inset: 0;
  pointer-events: none;
  z-index: 4;
}
.qs-illust-books {
  position: absolute;
  bottom: 20%;
  left: 16%;
  display: flex;
  gap: 4px;
  align-items: flex-end;
  z-index: 3;
  animation: qs-float 7s ease-in-out infinite 1s;
}
.qs-book {
  width: 14px;
  border-radius: 2px 4px 4px 2px;
  box-shadow: 2px 2px 4px rgba(0,0,0,.1);
}
.qs-illust-cap {
  position: absolute;
  top: 0;
  left: 50%;
  transform: translateX(-50%);
  z-index: 7;
  animation: qs-float 5s ease-in-out infinite 2s;
}
.qs-illust-plant {
  position: absolute;
  bottom: 16%;
  right: 14%;
  z-index: 3;
}
.qs-pot {
  width: 22px;
  height: 16px;
  background: #D97706;
  border-radius: 0 0 6px 6px;
  position: relative;
}
.qs-pot::before {
  content: '';
  position: absolute;
  top: -3px; left: -3px; right: -3px;
  height: 5px;
  background: #B45309;
  border-radius: 2px;
}
.qs-stem { width: 2px; height: 20px; background: #16A34A; margin: 0 auto; }
.qs-leaf {
  width: 14px;
  height: 8px;
  background: #22C55E;
  border-radius: 50% 0;
  position: absolute;
  top: -16px;
}
.qs-leaf-l { right: 11px; transform: rotate(-30deg); }
.qs-leaf-r { left: 11px; transform: rotate(30deg) scaleX(-1); }
.qs-illust-clip {
  position: absolute;
  top: 12%;
  right: 12%;
  z-index: 3;
  animation: qs-float 6.5s ease-in-out infinite .5s;
}
.qs-illust-pen {
  position: absolute;
  bottom: 14%;
  left: 26%;
  z-index: 3;
  transform: rotate(-20deg);
  animation: qs-float 5.5s ease-in-out infinite 1.5s;
}
.qs-star {
  position: absolute;
  z-index: 3;
  pointer-events: none;
  animation: qs-float var(--dur, 4s) ease-in-out infinite;
}
.qs-star svg { filter: drop-shadow(0 0 4px rgba(245,158,11,.3)); }
.qs-dot {
  position: absolute;
  width: 6px;
  height: 6px;
  border-radius: 50%;
  z-index: 2;
  pointer-events: none;
  animation: qs-float 5s ease-in-out infinite;
}

/* ==========================================================================
   8. EXAM BOARDS
   ========================================================================== */
.qs-boards { background: var(--qs-white); }
.qs-boards-row {
  display: grid;
  grid-template-columns: repeat(6, 1fr);
  gap: var(--qs-gap);
}
.qs-board {
  text-align: center;
  padding: 32px 12px;
  background: var(--qs-surface);
  border: 1px solid var(--qs-border);
  border-radius: var(--qs-r-md);
  transition: all .4s var(--qs-ease);
}
.qs-board:hover {
  transform: translateY(-6px);
  box-shadow: var(--qs-sh-3);
  border-color: var(--qs-blue-border);
}
.qs-board-icon {
  width: 52px;
  height: 52px;
  border-radius: var(--qs-r-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  margin: 0 auto 14px;
  color: #fff;
  font-size: 22px;
  font-weight: 800;
  box-shadow: var(--qs-sh-2);
  transition: transform .4s var(--qs-spring);
}
.qs-board:hover .qs-board-icon { transform: scale(1.1) rotate(-5deg); }
.qs-board h3 { font-size: 15px; font-weight: 700; margin-bottom: 4px; }
.qs-board p { font-size: 11px; color: var(--qs-muted); line-height: 1.4; }

/* ==========================================================================
   9. FEATURES
   ========================================================================== */
.qs-features { background: var(--qs-bg); }
.qs-features-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--qs-gap);
}
.qs-feat {
  background: var(--qs-surface);
  border: 1px solid var(--qs-border);
  border-radius: var(--qs-r-lg);
  padding: 36px 28px;
  transition: all .4s var(--qs-ease);
  position: relative;
  overflow: hidden;
}
.qs-feat:hover {
  transform: translateY(-6px);
  box-shadow: var(--qs-sh-4);
  border-color: var(--qs-blue-border);
}
.qs-feat-icon {
  width: 52px;
  height: 52px;
  border-radius: var(--qs-r-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 22px;
  transition: transform .3s var(--qs-spring);
}
.qs-feat:hover .qs-feat-icon { transform: scale(1.1) rotate(-5deg); }
.qs-feat h3 { font-size: 18px; font-weight: 700; margin-bottom: 10px; letter-spacing: -.01em; }
.qs-feat p { font-size: 14px; color: var(--qs-body); line-height: 1.65; margin-bottom: 16px; }
.qs-feat-link {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  font-size: 14px;
  font-weight: 600;
  color: var(--qs-blue);
  transition: gap .3s var(--qs-spring);
}
.qs-feat-link:hover { gap: 8px; }

/* ==========================================================================
   10. HOW IT WORKS — Horizontal Progress Timeline
   ========================================================================== */
.qs-how { background: var(--qs-white); }
.qs-how-content {
  display: grid;
  grid-template-columns: 1.2fr 1fr;
  gap: 60px;
  align-items: start;
}

/* Horizontal steps */
.qs-how-steps {
  display: grid;
  grid-template-columns: 1fr auto 1fr auto 1fr auto 1fr;
  align-items: start;
  gap: 0;
}
.qs-h-step {
  text-align: center;
  padding: 0 8px;
}
.qs-h-step-num {
  width: 48px;
  height: 48px;
  border-radius: 50%;
  background: var(--qs-blue);
  color: #fff;
  font-size: 18px;
  font-weight: 800;
  display: flex;
  align-items: center;
  justify-content: center;
  margin: 0 auto 16px;
  box-shadow: 0 4px 16px rgba(37,99,235,.3);
  transition: transform .3s var(--qs-spring);
  position: relative;
  z-index: 2;
}
.qs-h-step:hover .qs-h-step-num {
  transform: scale(1.1);
  box-shadow: 0 6px 24px rgba(37,99,235,.4);
}
.qs-h-step h3 {
  font-size: 15px;
  font-weight: 700;
  margin-bottom: 6px;
  color: var(--qs-heading);
}
.qs-h-step p {
  font-size: 13px;
  color: var(--qs-body);
  line-height: 1.5;
}
.qs-h-step-line {
  width: 100%;
  height: 2px;
  background: repeating-linear-gradient(90deg, var(--qs-blue-100) 0, var(--qs-blue-100) 6px, transparent 6px, transparent 12px);
  margin-top: 23px;
  flex-shrink: 1;
}

/* Stats card */
.qs-how-right {
  position: sticky;
  top: 120px;
}
.qs-stats-card {
  background: linear-gradient(135deg, #0F172A 0%, #1E293B 50%, #0F172A 100%);
  border-radius: var(--qs-r-lg);
  padding: 48px 40px;
  position: relative;
  overflow: hidden;
}
.qs-stats-card::before {
  content: '';
  position: absolute;
  top: -100px; right: -100px;
  width: 300px; height: 300px;
  background: radial-gradient(circle, rgba(37,99,235,.15), transparent 70%);
  pointer-events: none;
}
.qs-stats-card::after {
  content: '';
  position: absolute;
  bottom: -80px; left: -60px;
  width: 250px; height: 250px;
  background: radial-gradient(circle, rgba(139,92,246,.1), transparent 70%);
  pointer-events: none;
}
.qs-stats-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 32px;
  position: relative;
  z-index: 1;
}
.qs-st { text-align: center; }
.qs-st-num {
  font-size: clamp(32px, 4vw, 44px);
  font-weight: 800;
  color: #fff;
  letter-spacing: -.03em;
  line-height: 1;
}
.qs-st-sfx {
  font-size: clamp(24px, 3vw, 32px);
  font-weight: 700;
  color: var(--qs-blue-light);
  display: inline;
  line-height: 1;
}
.qs-st-label {
  font-size: 13px;
  color: rgba(255,255,255,.6);
  margin-top: 6px;
  font-weight: 500;
}

/* ==========================================================================
   11. TESTIMONIALS
   ========================================================================== */
.qs-testimonials { background: var(--qs-bg); }
.qs-test-header {
  display: flex;
  align-items: flex-end;
  justify-content: space-between;
  margin-bottom: 48px;
}
.qs-view-all {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 14px;
  font-weight: 600;
  color: var(--qs-blue);
  white-space: nowrap;
  transition: gap .3s var(--qs-spring);
  flex-shrink: 0;
}
.qs-view-all:hover { gap: 10px; }
.qs-test-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--qs-gap);
}
.qs-test {
  background: var(--qs-surface);
  border: 1px solid var(--qs-border);
  border-radius: var(--qs-r-lg);
  padding: 32px;
  transition: all .4s var(--qs-ease);
}
.qs-test:hover {
  transform: translateY(-4px);
  box-shadow: var(--qs-sh-3);
}
.qs-test-stars {
  color: #F59E0B;
  font-size: 16px;
  letter-spacing: 2px;
  margin-bottom: 16px;
}
.qs-test blockquote {
  font-size: 15px;
  line-height: 1.7;
  color: var(--qs-body-dark);
  margin-bottom: 20px;
  font-style: normal;
}
.qs-test-author {
  display: flex;
  align-items: center;
  gap: 12px;
}
.qs-test-av {
  width: 42px;
  height: 42px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  color: #fff;
  font-size: 14px;
  font-weight: 700;
  flex-shrink: 0;
}
.qs-test-author strong { display: block; font-size: 14px; font-weight: 700; }
.qs-test-author span { font-size: 12px; color: var(--qs-muted); }
.qs-dots {
  display: flex;
  justify-content: center;
  gap: 8px;
  margin-top: 40px;
}
.qs-dot-ind {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--qs-border);
  transition: all .3s;
  cursor: pointer;
}
.qs-dot-ind.active {
  background: var(--qs-blue);
  width: 24px;
  border-radius: 4px;
}

/* ==========================================================================
   12. CTA
   ========================================================================== */
.qs-cta { background: var(--qs-white); }
.qs-cta-banner {
  background: linear-gradient(135deg, #2563EB 0%, #3B82F6 40%, #6366F1 100%);
  border-radius: var(--qs-r-lg);
  padding: 72px 56px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 48px;
  position: relative;
  overflow: hidden;
}
.qs-cta-banner::before {
  content: '';
  position: absolute;
  top: -80px; right: -80px;
  width: 300px; height: 300px;
  border-radius: 50%;
  background: rgba(255,255,255,.06);
  pointer-events: none;
}
.qs-cta-banner::after {
  content: '';
  position: absolute;
  bottom: -60px; left: -60px;
  width: 250px; height: 250px;
  border-radius: 50%;
  background: rgba(255,255,255,.04);
  pointer-events: none;
}
.qs-cta-left {
  position: relative;
  z-index: 1;
  flex: 1;
  max-width: 560px;
}
.qs-cta-left h2 {
  font-size: clamp(28px, 3.5vw, 40px);
  font-weight: 800;
  color: #fff;
  letter-spacing: -.03em;
  margin-bottom: 14px;
  line-height: 1.15;
}
.qs-cta-left p {
  font-size: 17px;
  color: rgba(255,255,255,.85);
  line-height: 1.65;
  margin-bottom: 28px;
}
.qs-cta-form {
  display: flex;
  gap: 10px;
  max-width: 440px;
}
.qs-cta-input {
  flex: 1;
  padding: 14px 18px;
  border-radius: var(--qs-r-sm);
  border: 1.5px solid rgba(255,255,255,.2);
  background: rgba(255,255,255,.1);
  color: #fff;
  font-size: 15px;
  outline: none;
  transition: border-color .2s;
}
.qs-cta-input::placeholder { color: rgba(255,255,255,.6); }
.qs-cta-input:focus { border-color: rgba(255,255,255,.5); background: rgba(255,255,255,.15); }
.qs-cta-submit {
  padding: 14px 28px;
  font-size: 15px;
  font-weight: 700;
  color: var(--qs-blue);
  background: #fff;
  border-radius: var(--qs-r-sm);
  transition: all .3s var(--qs-ease);
  white-space: nowrap;
  box-shadow: 0 2px 8px rgba(0,0,0,.1);
}
.qs-cta-submit:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(0,0,0,.15);
}
.qs-cta-mascot {
  position: relative;
  z-index: 2;
  flex-shrink: 0;
  animation: qs-float 5s ease-in-out infinite;
}

/* ==========================================================================
   13. FOOTER — 6 Columns
   ========================================================================== */
.qs-footer {
  background: var(--qs-navy);
  color: rgba(255,255,255,.7);
  padding: 72px 0 0;
}
.qs-footer-grid {
  display: grid;
  grid-template-columns: 1.5fr 1fr 1fr 1fr 1fr 1.2fr;
  gap: 40px;
  padding-bottom: 48px;
}
.qs-ft-logo {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-bottom: 16px;
  color: #fff;
}
.qs-ft-logo span { font-size: 18px; font-weight: 800; }
.qs-ft-brand p {
  font-size: 14px;
  line-height: 1.7;
  margin-bottom: 20px;
  color: rgba(255,255,255,.5);
}
.qs-ft-social { display: flex; gap: 10px; }
.qs-ft-social a {
  width: 36px;
  height: 36px;
  border-radius: var(--qs-r-xs);
  border: 1px solid rgba(255,255,255,.1);
  display: flex;
  align-items: center;
  justify-content: center;
  color: rgba(255,255,255,.5);
  transition: all .25s;
}
.qs-ft-social a:hover {
  border-color: var(--qs-blue-light);
  color: var(--qs-blue-light);
  background: rgba(37,99,235,.1);
  transform: translateY(-2px);
}
.qs-ft-col h4 {
  font-size: 13px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: .08em;
  color: #fff;
  margin-bottom: 18px;
}
.qs-ft-col a {
  display: block;
  font-size: 14px;
  color: rgba(255,255,255,.5);
  padding: 5px 0;
  transition: all .2s;
}
.qs-ft-col a:hover { color: #fff; transform: translateX(4px); }
.qs-ft-newsletter p {
  font-size: 14px;
  color: rgba(255,255,255,.5);
  margin-bottom: 14px;
  line-height: 1.6;
}
.qs-nl-form { display: flex; gap: 8px; }
.qs-nl-input {
  flex: 1;
  padding: 10px 14px;
  border-radius: var(--qs-r-xs);
  border: 1px solid rgba(255,255,255,.15);
  background: rgba(255,255,255,.06);
  color: #fff;
  font-size: 13px;
  outline: none;
  transition: border-color .2s;
}
.qs-nl-input::placeholder { color: rgba(255,255,255,.35); }
.qs-nl-input:focus { border-color: var(--qs-blue-light); }
.qs-nl-btn {
  padding: 10px 18px;
  font-size: 13px;
  font-weight: 600;
  color: #fff;
  background: var(--qs-blue);
  border-radius: var(--qs-r-xs);
  transition: all .2s;
  white-space: nowrap;
}
.qs-nl-btn:hover { background: var(--qs-blue-dark); }
.qs-footer-bar {
  border-top: 1px solid rgba(255,255,255,.08);
  padding: 24px 0;
  display: flex;
  align-items: center;
  justify-content: space-between;
}
.qs-footer-bar p { font-size: 13px; color: rgba(255,255,255,.35); }
.qs-lang {
  padding: 6px 12px;
  border-radius: var(--qs-r-xs);
  border: 1px solid rgba(255,255,255,.15);
  background: transparent;
  color: rgba(255,255,255,.5);
  font-size: 13px;
  cursor: pointer;
  outline: none;
}
.qs-lang option { background: var(--qs-navy); color: #fff; }

/* ==========================================================================
   14. MOBILE BOTTOM NAVIGATION
   ========================================================================== */
.qs-mob-bottom {
  display: none;
  position: fixed;
  bottom: 0;
  left: 0;
  right: 0;
  z-index: 999;
  background: rgba(255,255,255,.95);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border-top: 1px solid var(--qs-border);
  padding: 8px 0 calc(8px + env(safe-area-inset-bottom, 0px));
  box-shadow: 0 -2px 12px rgba(0,0,0,.05);
}
.qs-mb-item {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 2px;
  font-size: 10px;
  font-weight: 500;
  color: var(--qs-muted);
  transition: color .2s;
  text-decoration: none;
  padding: 4px 0;
  flex: 1;
}
.qs-mb-item svg { transition: transform .3s var(--qs-spring); }
.qs-mb-item.active,
.qs-mb-item:hover {
  color: var(--qs-blue);
}
.qs-mb-item.active svg,
.qs-mb-item:hover svg {
  transform: scale(1.1);
}

/* ==========================================================================
   15. RESPONSIVE — 1024px
   ========================================================================== */
@media (max-width: 1024px) {
  .qs-desktop-nav,
  .qs-actions .qs-btn-login,
  .qs-actions .qs-btn-cta-sm,
  .qs-actions .qs-icon-btn { display: none; }
  .qs-hamburger { display: flex; }

  .qs-hero-grid {
    grid-template-columns: 1fr;
    text-align: center;
  }
  .qs-hero-left { max-width: 100%; margin: 0 auto; }
  .qs-badge { margin-left: auto; margin-right: auto; }
  .qs-hero-btns { justify-content: center; }
  .qs-checks { justify-content: center; }
  .qs-social { justify-content: center; }
  .qs-hero-right { margin-top: 40px; }
  .qs-illust { max-width: 480px; margin: 0 auto; }

  .qs-boards-row { grid-template-columns: repeat(3, 1fr); }
  .qs-features-grid { grid-template-columns: repeat(2, 1fr); }
  .qs-how-content { grid-template-columns: 1fr; gap: 48px; }
  .qs-how-steps { grid-template-columns: 1fr auto 1fr auto 1fr auto 1fr; }
  .qs-how-right { position: static; }
  .qs-test-header { flex-direction: column; align-items: flex-start; gap: 12px; }
  .qs-test-grid { grid-template-columns: repeat(2, 1fr); }
  .qs-test-grid .qs-test:last-child { display: none; }
  .qs-footer-grid { grid-template-columns: repeat(3, 1fr); }
}

/* ==========================================================================
   16. RESPONSIVE — 768px
   ========================================================================== */
@media (max-width: 768px) {
  :root { --qs-section: 80px; }
  .qs-hero { padding: 120px 0 60px; min-height: auto; }
  .qs-hero-title { font-size: 48px; }
  .qs-hero-btns { flex-direction: column; align-items: center; }
  .qs-btn-hero, .qs-btn-hero-outline { width: 100%; max-width: 320px; justify-content: center; }
  .qs-checks { flex-direction: column; align-items: center; gap: 10px; }

  .qs-boards-row { grid-template-columns: repeat(2, 1fr); }
  .qs-features-grid { grid-template-columns: 1fr; }

  /* Horizontal timeline stacks on tablet */
  .qs-how-steps {
    grid-template-columns: 1fr;
    gap: 0;
  }
  .qs-h-step {
    display: grid;
    grid-template-columns: 48px 1fr;
    gap: 16px;
    text-align: left;
    padding: 0 0 24px;
    position: relative;
  }
  .qs-h-step-num { grid-row: 1 / 3; margin: 0; }
  .qs-h-step h3 { margin-bottom: 2px; }
  .qs-h-step-line {
    width: 2px;
    height: 24px;
    margin: 0 0 0 23px;
    background: repeating-linear-gradient(180deg, var(--qs-blue-100) 0, var(--qs-blue-100) 6px, transparent 6px, transparent 12px);
  }

  .qs-stats-grid { grid-template-columns: repeat(2, 1fr); gap: 24px; }
  .qs-test-header { flex-direction: column; align-items: flex-start; }
  .qs-test-grid { grid-template-columns: 1fr; }
  .qs-test-grid .qs-test:last-child { display: block; }

  .qs-cta-banner {
    flex-direction: column;
    text-align: center;
    padding: 48px 24px;
  }
  .qs-cta-form { flex-direction: column; }
  .qs-cta-mascot { margin: 0 auto; }

  .qs-footer-grid { grid-template-columns: repeat(2, 1fr); gap: 32px; }
  .qs-ft-brand { grid-column: 1 / -1; }
  .qs-footer-bar { flex-direction: column; gap: 16px; text-align: center; }

  /* Show mobile bottom nav */
  .qs-mob-bottom { display: flex; }
  body.qs { padding-bottom: 72px; }
}

/* ==========================================================================
   17. RESPONSIVE — 480px
   ========================================================================== */
@media (max-width: 480px) {
  .qs-container { padding: 0 16px; }
  .qs-hero-title { font-size: 38px; }
  .qs-hero-desc { font-size: 16px; }
  .qs-boards-row { grid-template-columns: repeat(2, 1fr); gap: 10px; }
  .qs-board { padding: 24px 8px; }
  .qs-heading { font-size: 26px; }
  .qs-footer-grid { grid-template-columns: 1fr; }
  .qs-stats-card { padding: 32px 24px; }
  .qs-stats-grid { grid-template-columns: repeat(2, 1fr); gap: 20px; }
  .qs-laptop { width: 220px; }
  .qs-illust-books, .qs-illust-plant, .qs-illust-clip, .qs-illust-pen { display: none; }
  .qs-how-steps { grid-template-columns: 1fr; }
}

/* ==========================================================================
   18. DARK MODE
   ========================================================================== */
body.qs-dark {
  --qs-white: #0F172A;
  --qs-bg: #1E293B;
  --qs-surface: #1E293B;
  --qs-heading: #F1F5F9;
  --qs-body: #94A3B8;
  --qs-body-dark: #CBD5E1;
  --qs-muted: #64748B;
  --qs-border: #334155;
  --qs-border-light: #1E293B;
  color-scheme: dark;
}
body.qs-dark .qs-header { background: #0F172A; }
body.qs-dark .qs-header.scrolled { box-shadow: 0 1px 0 rgba(255,255,255,.06); background: rgba(15,23,42,.85); }
body.qs-dark .qs-dropdown { background: #1E293B; border-color: #334155; }
body.qs-dark .qs-mobile { background: rgba(15,23,42,.97); }
body.qs-dark .qs-board,
body.qs-dark .qs-feat,
body.qs-dark .qs-test { background: #1E293B; border-color: #334155; }
body.qs-dark .qs-fcard { background: #1E293B; border-color: #334155; color: #F1F5F9; }
body.qs-dark .qs-nav-link:hover,
body.qs-dark .qs-nav-link.active { background: rgba(255,255,255,.06); }
body.qs-dark .qs-m-link:hover { background: rgba(255,255,255,.05); }
body.qs-dark .qs-icon-btn:hover { background: rgba(255,255,255,.06); }
body.qs-dark .qs-hamburger:hover { background: rgba(255,255,255,.06); }
body.qs-dark .qs-mob-bottom { background: rgba(15,23,42,.95); border-color: #334155; }

/* ==========================================================================
   19. REDUCED MOTION
   ========================================================================== */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: .01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: .01ms !important;
  }
  html { scroll-behavior: auto; }
  body.qs-js .qs-r { opacity: 1; transform: none; }
}