/* Design system "Luyện Tập IELTS" v2 - phong cách gradient hiện đại (kiểu
   Stripe/Linear/Vercel): hero nền tối có gradient mesh rực rỡ tạo điểm nhấn
   thị giác mạnh ngay từ đầu, phần còn lại nền sáng với icon-badge gradient +
   card có chiều sâu (shadow màu, viền gradient khi hover) thay vì phẳng. */
:root {
  --bg: #FFFFFF;
  --bg-alt: #F8F7FF;
  --card: #FFFFFF;
  --ink: #0F172A;
  --text-muted: #64748B;
  --primary: #4F46E5;
  --primary-dark: #3730A3;
  --accent: #06B6D4;
  --accent-2: #A855F7;
  --border: #E5E7EB;
  --tint: #EEF2FF;
  --green: #16A34A;
  --green-container: #DCFCE7;
  --red: #DC2626;
  --shadow: 0 4px 24px rgba(15, 23, 42, 0.06);
  --shadow-md: 0 20px 40px rgba(79, 70, 229, 0.16);
  --radius: 16px;
  --grad-brand: linear-gradient(135deg, var(--primary) 0%, var(--accent) 100%);
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: 'Be Vietnam Pro', -apple-system, Segoe UI, Roboto, Arial, sans-serif;
  background: var(--bg);
  color: var(--ink);
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
}

h1, h2, h3 {
  font-family: 'Be Vietnam Pro', -apple-system, Segoe UI, Roboto, Arial, sans-serif;
  font-weight: 800;
  letter-spacing: -0.02em;
  color: var(--ink);
  line-height: 1.2;
}

a { color: var(--primary); }

.container {
  max-width: 1080px;
  margin: 0 auto;
  padding: 0 20px;
}

/* ---- Icon badge (SVG line-art trắng trên nền gradient thương hiệu) ---- */
.icon-badge {
  width: 52px;
  height: 52px;
  border-radius: 14px;
  background: var(--grad-brand);
  color: #fff;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 16px;
  flex-shrink: 0;
  box-shadow: 0 10px 20px -6px rgba(79, 70, 229, 0.45);
}
.icon-badge svg { width: 26px; height: 26px; }
.icon-badge.lg { width: 64px; height: 64px; border-radius: 18px; }
.icon-badge.lg svg { width: 32px; height: 32px; }

.page-header { display: flex; align-items: center; gap: 18px; margin-bottom: 4px; }
.page-header .icon-badge { margin-bottom: 0; }
.page-header h1 { margin: 0; }

/* ---- Eyebrow (nhãn nhỏ phía trên tiêu đề section) ---- */
.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-weight: 700;
  font-size: 0.8em;
  letter-spacing: 0.02em;
  text-transform: uppercase;
  color: var(--primary);
  background: var(--tint);
  padding: 6px 14px;
  border-radius: 999px;
  margin-bottom: 14px;
}
.eyebrow svg { width: 14px; height: 14px; }

/* ---- Header / nav ---- */
header.site-header {
  background: rgba(255, 255, 255, 0.85);
  backdrop-filter: saturate(180%) blur(10px);
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  z-index: 10;
}
.nav-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 14px 0;
}
.brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  font-size: 1.15em;
  font-weight: 800;
  color: var(--ink);
  text-decoration: none;
  letter-spacing: -0.01em;
}
.brand .brand-mark {
  width: 34px;
  height: 34px;
  border-radius: 10px;
  background: var(--grad-brand);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  box-shadow: 0 6px 14px -4px rgba(79, 70, 229, 0.5);
}
.brand .brand-mark svg { width: 19px; height: 19px; color: #fff; }
nav.main-nav {
  display: flex;
  align-items: center;
  gap: 4px;
  flex-wrap: wrap;
}
nav.main-nav a {
  color: var(--text-muted);
  text-decoration: none;
  font-weight: 600;
  font-size: 0.94em;
  padding: 9px 15px;
  border-radius: 8px;
  transition: background 0.15s, color 0.15s;
}
nav.main-nav a:hover { color: var(--primary); background: var(--tint); }
nav.main-nav a[data-auth="guest"], nav.main-nav a[data-auth="user"] {
  color: #fff !important;
  background: var(--grad-brand);
  margin-left: 6px;
  box-shadow: 0 4px 12px -3px rgba(79, 70, 229, 0.5);
}
nav.main-nav a[data-auth="guest"]:hover, nav.main-nav a[data-auth="user"]:hover { opacity: 0.9; }
.nav-toggle { display: none; }
@media (max-width: 720px) {
  nav.main-nav { display: none; flex-direction: column; align-items: stretch; gap: 6px; width: 100%; padding-bottom: 14px; }
  nav.main-nav.open { display: flex; }
  nav.main-nav a { text-align: left; }
  nav.main-nav a[data-auth="guest"], nav.main-nav a[data-auth="user"] { margin-left: 0; text-align: center; }
  .nav-toggle {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    background: none;
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 8px 12px;
    cursor: pointer;
    color: var(--ink);
  }
  .nav-toggle svg { width: 22px; height: 22px; display: block; }
  .nav-row { flex-wrap: wrap; }
}

/* ---- Hero: nền tối gradient mesh, điểm nhấn thị giác chính của trang ---- */
.hero {
  position: relative;
  overflow: hidden;
  text-align: center;
  padding: 108px 20px 96px;
  background:
    radial-gradient(900px 480px at 15% -15%, rgba(168, 85, 247, 0.45), transparent 60%),
    radial-gradient(800px 500px at 100% 10%, rgba(6, 182, 212, 0.40), transparent 60%),
    radial-gradient(700px 400px at 50% 120%, rgba(79, 70, 229, 0.35), transparent 60%),
    linear-gradient(180deg, #0B1120 0%, #151233 55%, #0B1120 100%);
  color: #fff;
}
.hero::before {
  content: '';
  position: absolute;
  inset: 0;
  background-image: radial-gradient(rgba(255,255,255,0.09) 1px, transparent 1px);
  background-size: 26px 26px;
  mask-image: radial-gradient(ellipse 700px 400px at 50% 20%, black, transparent 75%);
  pointer-events: none;
}
.hero > * { position: relative; z-index: 1; }
.hero-eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  background: rgba(255, 255, 255, 0.08);
  border: 1px solid rgba(255, 255, 255, 0.18);
  backdrop-filter: blur(6px);
  color: #fff;
  font-weight: 700;
  font-size: 0.84em;
  padding: 8px 18px;
  border-radius: 999px;
  margin-bottom: 24px;
}
.hero-eyebrow svg { width: 15px; height: 15px; color: #67E8F9; }
.hero h1 { font-size: 2.9em; margin: 0 0 18px; color: #fff; letter-spacing: -0.02em; }
.hero h1 .grad {
  background: linear-gradient(90deg, #C084FC, #67E8F9);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}
.hero p.subtitle { font-size: 1.18em; color: rgba(255, 255, 255, 0.72); max-width: 640px; margin: 0 auto 36px; }
.hero .btn-outline {
  background: rgba(255, 255, 255, 0.06);
  color: #fff !important;
  border-color: rgba(255, 255, 255, 0.3);
}
.hero .btn-outline:hover { background: rgba(255, 255, 255, 0.14); border-color: rgba(255, 255, 255, 0.5); }
.trust-row {
  display: flex;
  justify-content: center;
  gap: 32px;
  flex-wrap: wrap;
  margin-top: 44px;
  color: rgba(255, 255, 255, 0.62);
  font-size: 0.88em;
  font-weight: 600;
}
.trust-row span { display: inline-flex; align-items: center; gap: 8px; }
.trust-row svg { width: 17px; height: 17px; color: #67E8F9; }

/* ---- Hero layout: chữ bên trái, hình minh hoạ (mockup giao diện luyện
   thi) bên phải - dựng bằng HTML/CSS thuần, không phụ thuộc ảnh/thư viện
   ngoài, để tạo ngữ cảnh sinh động thay vì chỉ toàn chữ. ---- */
.hero-grid { display: grid; grid-template-columns: 1.05fr 0.95fr; gap: 52px; align-items: center; text-align: left; }
.hero-copy .btn-row, .hero-copy .trust-row { justify-content: flex-start; }
@media (max-width: 900px) {
  .hero-grid { grid-template-columns: 1fr; text-align: center; }
  .hero-copy .btn-row, .hero-copy .trust-row { justify-content: center; }
  .hero-visual { margin: 44px auto 0; max-width: 380px; }
}

.hero-visual { position: relative; }
.mock-window {
  background: rgba(255, 255, 255, 0.07);
  border: 1px solid rgba(255, 255, 255, 0.16);
  border-radius: 18px;
  backdrop-filter: blur(8px);
  box-shadow: 0 40px 70px -24px rgba(0, 0, 0, 0.55);
}
.mock-window-bar { display: flex; gap: 6px; padding: 14px 18px; border-bottom: 1px solid rgba(255, 255, 255, 0.12); }
.mock-window-bar span { width: 10px; height: 10px; border-radius: 50%; background: rgba(255, 255, 255, 0.25); }
.mock-window-body { padding: 22px 22px 26px; }
.mock-pill {
  display: inline-block;
  background: linear-gradient(90deg, #C084FC, #67E8F9);
  color: #0B1120;
  font-weight: 700;
  font-size: 0.72em;
  padding: 4px 12px;
  border-radius: 999px;
  margin-bottom: 16px;
}
.mock-line { height: 10px; border-radius: 6px; background: rgba(255, 255, 255, 0.16); margin-bottom: 12px; }
.mock-line.w-100 { width: 100%; }
.mock-line.w-80 { width: 80%; }
.mock-line.w-55 { width: 55%; }
.mock-options { display: flex; flex-direction: column; gap: 9px; margin: 18px 0 20px; }
.mock-option {
  display: flex;
  align-items: center;
  gap: 11px;
  padding: 10px 13px;
  border: 1px solid rgba(255, 255, 255, 0.14);
  border-radius: 10px;
  font-size: 0.87em;
  color: rgba(255, 255, 255, 0.75);
}
.mock-option .dot { width: 16px; height: 16px; border-radius: 50%; border: 2px solid rgba(255, 255, 255, 0.35); flex-shrink: 0; }
.mock-option.correct { border-color: rgba(103, 232, 249, 0.55); background: rgba(103, 232, 249, 0.1); color: #fff; }
.mock-option.correct .dot { border-color: #67E8F9; background: #67E8F9; }
.mock-progress-track { height: 6px; background: rgba(255, 255, 255, 0.16); border-radius: 4px; overflow: hidden; }
.mock-progress-fill { height: 100%; width: 74%; background: linear-gradient(90deg, #C084FC, #67E8F9); }
.mock-progress-label { display: flex; justify-content: space-between; font-size: 0.76em; color: rgba(255, 255, 255, 0.55); margin-top: 8px; }

.mock-float {
  position: absolute;
  display: flex;
  align-items: center;
  gap: 11px;
  background: #fff;
  color: var(--ink);
  border-radius: 14px;
  padding: 12px 16px;
  box-shadow: 0 18px 36px -10px rgba(15, 23, 42, 0.4);
  font-size: 0.85em;
}
.mock-float .icon-badge { width: 36px; height: 36px; border-radius: 10px; margin: 0; box-shadow: none; }
.mock-float .icon-badge svg { width: 19px; height: 19px; }
.mock-float-title { font-weight: 700; }
.mock-float-sub { color: var(--text-muted); font-size: 0.92em; }
.mock-float-band { top: -22px; right: -18px; }
.mock-float-listen { bottom: -20px; left: -22px; }
@media (max-width: 900px) {
  .mock-float-band { top: -16px; right: -8px; }
  .mock-float-listen { bottom: -16px; left: -8px; }
}
@media (max-width: 420px) {
  .mock-float { padding: 9px 12px; font-size: 0.78em; }
}

/* ---- Buttons ---- */
.btn {
  display: inline-block;
  background: var(--grad-brand);
  color: #fff !important;
  text-decoration: none;
  padding: 14px 30px;
  border-radius: 12px;
  font-weight: 700;
  font-size: 0.98em;
  border: none;
  cursor: pointer;
  transition: transform 0.15s, box-shadow 0.15s, filter 0.15s;
  box-shadow: 0 10px 24px -6px rgba(79, 70, 229, 0.5);
}
.btn:hover { transform: translateY(-2px); filter: brightness(1.06); box-shadow: 0 14px 30px -6px rgba(79, 70, 229, 0.6); }
.btn-outline {
  display: inline-block;
  background: var(--card);
  color: var(--ink) !important;
  text-decoration: none;
  padding: 13px 29px;
  border-radius: 12px;
  font-weight: 700;
  font-size: 0.98em;
  border: 1.5px solid var(--border);
  cursor: pointer;
  transition: border-color 0.15s, background 0.15s, transform 0.15s;
}
.btn-outline:hover { border-color: var(--primary); background: var(--tint); transform: translateY(-2px); }
.btn-row { display: flex; gap: 14px; justify-content: center; flex-wrap: wrap; }
.btn:disabled, .btn-outline:disabled { opacity: 0.6; cursor: not-allowed; transform: none; }

/* ---- Cards / sections ---- */
.card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 26px;
  box-shadow: var(--shadow);
}
.card + .card { margin-top: 16px; }
section { padding: 72px 0; position: relative; }
section.section-alt { background: var(--bg-alt); }
.section-head { text-align: center; max-width: 620px; margin: 0 auto 12px; }
.section-head h2 { font-size: 2em; margin-bottom: 10px; }
.section-head p { color: var(--text-muted); font-size: 1.05em; margin: 0; }

.grid-cards {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 22px;
  margin-top: 36px;
}
.skill-card {
  position: relative;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 26px;
  text-decoration: none;
  color: var(--ink);
  box-shadow: var(--shadow);
  transition: transform 0.2s, box-shadow 0.2s, border-color 0.2s;
  display: block;
  overflow: hidden;
}
.skill-card::before {
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 3px;
  background: var(--grad-brand);
  transform: scaleX(0);
  transform-origin: left;
  transition: transform 0.25s;
}
.skill-card:hover { transform: translateY(-6px); box-shadow: var(--shadow-md); border-color: transparent; }
.skill-card:hover::before { transform: scaleX(1); }
.skill-card h3 { margin: 0 0 6px; color: var(--ink); font-size: 1.14em; font-weight: 700; }
.skill-card p { margin: 0; font-size: 0.92em; color: var(--text-muted); }

/* ---- Forms ---- */
label { display: block; font-weight: 700; margin-bottom: 6px; color: var(--ink); font-size: 0.92em; }
input[type=email], input[type=password], input[type=text], textarea, select {
  width: 100%;
  padding: 12px 14px;
  border: 1px solid var(--border);
  border-radius: 10px;
  font-size: 1em;
  font-family: inherit;
  margin-bottom: 16px;
  background: var(--card);
  color: var(--ink);
}
input:focus, textarea:focus, select:focus { outline: none; border-color: var(--primary); box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.14); }
.form-narrow { max-width: 420px; margin: 0 auto; }

.note {
  background: #FFFBEB;
  border: 1px solid #FDE68A;
  color: #92400E;
  border-radius: 10px;
  padding: 12px 16px;
  font-size: 0.94em;
  margin: 16px 0;
}
.badge-paid { background: var(--green-container); color: var(--green); padding: 4px 12px; border-radius: 20px; font-weight: 700; font-size: 0.85em; }
.badge-free { background: var(--tint); color: var(--primary); padding: 4px 12px; border-radius: 20px; font-weight: 700; font-size: 0.85em; }
.error-msg { color: var(--red); font-size: 0.92em; margin-top: -8px; margin-bottom: 12px; }
.success-msg { color: var(--green); font-weight: 600; }

.cta-banner {
  text-align: center;
  padding: 56px 32px;
  border-radius: 24px;
  background:
    radial-gradient(600px 300px at 15% 0%, rgba(168, 85, 247, 0.35), transparent 60%),
    radial-gradient(600px 300px at 100% 100%, rgba(6, 182, 212, 0.35), transparent 60%),
    linear-gradient(135deg, #1E1B4B 0%, #0B1120 100%);
  color: #fff;
}
.cta-banner h2 { color: #fff; margin: 0 0 8px; }
.cta-banner p { color: rgba(255, 255, 255, 0.72); margin: 0 0 24px; }

footer {
  border-top: 1px solid var(--border);
  margin-top: 40px;
  padding: 32px 0;
  color: var(--text-muted);
  font-size: 0.88em;
  text-align: center;
}
footer a { color: var(--text-muted); }

.steps { padding-left: 1.3em; }
.steps li { margin-bottom: 10px; }
.divider { height: 1px; background: var(--border); margin: 32px 0; border: none; }