/* ТЕХСПЕЦ.PRO — видеоуроки. Базовые стили, без внешних шрифтов/зависимостей для максимальной скорости загрузки. */

:root {
  --blue: #2e5bff;
  --blue-dark: #1a3fd6;
  --blue-light: #eaf0ff;
  --bg: #f6f7fb;
  --card: #ffffff;
  --ink: #12172b;
  --ink-soft: #4b5266;
  --gray: #6b7280;
  --border: #e6e8f0;
  --radius-lg: 18px;
  --radius-md: 12px;
  --shadow: 0 2px 10px rgba(18, 23, 43, 0.05), 0 12px 32px -16px rgba(18, 23, 43, 0.12);
  --container: 1080px;
}

* {
  box-sizing: border-box;
}

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  background: var(--bg);
  color: var(--ink);
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
}

img, video {
  max-width: 100%;
  display: block;
}

a {
  color: inherit;
}

.container {
  max-width: var(--container);
  margin: 0 auto;
  padding: 0 20px;
}

/* ---------- Header ---------- */

.site-header {
  position: sticky;
  top: 0;
  z-index: 40;
  background: rgba(246, 247, 251, 0.92);
  backdrop-filter: saturate(180%) blur(10px);
  border-bottom: 1px solid var(--border);
}

.site-header__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
  max-width: var(--container);
  margin: 0 auto;
  padding: 0 20px;
}

.logo {
  display: flex;
  align-items: baseline;
  gap: 2px;
  font-weight: 800;
  font-size: 18px;
  letter-spacing: -0.02em;
  text-decoration: none;
  color: var(--ink);
}

.logo span {
  color: var(--blue);
}

.lesson-dots {
  display: flex;
  gap: 8px;
}

.lesson-dots a {
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background: var(--border);
  text-decoration: none;
  transition: transform 0.15s ease, background 0.15s ease;
}

.lesson-dots a:hover {
  transform: scale(1.2);
}

.lesson-dots a.is-current {
  background: var(--blue);
  width: 24px;
  border-radius: 6px;
}

.lesson-dots a.is-done {
  background: #b7c4ff;
}

@media (max-width: 640px) {
  .lesson-dots {
    gap: 6px;
  }
  .lesson-dots a {
    width: 8px;
    height: 8px;
  }
  .lesson-dots a.is-current {
    width: 18px;
  }
}

/* ---------- Breadcrumb / hero ---------- */

.lesson-hero {
  padding: 28px 0 20px;
}

.breadcrumb {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 13px;
  color: var(--gray);
  margin-bottom: 14px;
  flex-wrap: wrap;
}

.breadcrumb a {
  text-decoration: none;
  color: var(--gray);
}

.breadcrumb a:hover {
  color: var(--blue);
}

.badge {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  background: var(--blue);
  color: #fff;
  font-weight: 700;
  font-size: 13px;
  padding: 5px 12px;
  border-radius: 999px;
  letter-spacing: 0.01em;
}

.lesson-hero h1 {
  font-size: clamp(24px, 4vw, 34px);
  line-height: 1.2;
  letter-spacing: -0.02em;
  margin: 0 0 8px;
}

.lesson-hero__sub {
  color: var(--ink-soft);
  font-size: 16px;
  max-width: 640px;
  margin: 0;
}

/* ---------- Video ---------- */

.video-section {
  margin: 20px 0 8px;
}

.video-wrap {
  position: relative;
  width: 100%;
  aspect-ratio: 16 / 9;
  background: #0c0f1e;
  border-radius: var(--radius-lg);
  overflow: hidden;
  box-shadow: var(--shadow);
}

.video-wrap video {
  width: 100%;
  height: 100%;
  object-fit: cover;
  background: #0c0f1e;
}

.video-fallback {
  position: absolute;
  inset: 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 10px;
  color: #fff;
  background: linear-gradient(135deg, #1a2140 0%, #0c0f1e 60%);
  text-align: center;
  padding: 20px;
  pointer-events: none;
}

.video-fallback .play-icon {
  width: 56px;
  height: 56px;
  border-radius: 50%;
  background: var(--blue);
  display: flex;
  align-items: center;
  justify-content: center;
}

.video-fallback .play-icon svg {
  width: 20px;
  height: 20px;
  fill: #fff;
  margin-left: 3px;
}

.video-fallback strong {
  font-size: 15px;
  font-weight: 700;
}

.video-fallback span {
  font-size: 13px;
  color: #b6bdd6;
  max-width: 320px;
}

.video-meta {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 12px;
  margin-top: 10px;
  font-size: 12px;
  color: var(--gray);
  flex-wrap: wrap;
}

/* ---------- Content grid ---------- */

.content-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 16px;
  margin: 24px 0;
}

@media (min-width: 800px) {
  .content-grid {
    grid-template-columns: 1.1fr 0.9fr;
    align-items: start;
  }
}

.card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 22px 24px;
}

.card h2 {
  font-size: 18px;
  margin: 0 0 12px;
  letter-spacing: -0.01em;
}

.card h2 .num {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 26px;
  height: 26px;
  border-radius: 8px;
  background: var(--blue-light);
  color: var(--blue);
  font-size: 13px;
  font-weight: 800;
  margin-right: 8px;
  vertical-align: middle;
}

.card p {
  margin: 0 0 10px;
  color: var(--ink-soft);
  font-size: 15px;
}

.card ul.key-points {
  margin: 12px 0 0;
  padding: 0;
  list-style: none;
  display: grid;
  gap: 8px;
}

.card ul.key-points li {
  display: flex;
  gap: 10px;
  font-size: 14px;
  color: var(--ink-soft);
}

.card ul.key-points li::before {
  content: "";
  flex: none;
  width: 6px;
  height: 6px;
  margin-top: 7px;
  border-radius: 50%;
  background: var(--blue);
}

.steps {
  list-style: none;
  margin: 0;
  padding: 0;
  counter-reset: step;
  display: grid;
  gap: 14px;
}

.steps li {
  counter-increment: step;
  display: flex;
  gap: 12px;
  font-size: 14.5px;
  color: var(--ink-soft);
}

.steps li::before {
  content: counter(step);
  flex: none;
  width: 26px;
  height: 26px;
  border-radius: 50%;
  background: var(--blue);
  color: #fff;
  font-weight: 700;
  font-size: 13px;
  display: flex;
  align-items: center;
  justify-content: center;
}

.steps li strong {
  color: var(--ink);
  display: block;
  font-size: 14.5px;
}

/* ---------- Promo box ---------- */

.promo-box {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  background: var(--ink);
  color: #fff;
  border-radius: var(--radius-lg);
  padding: 20px 24px;
  margin: 24px 0;
}

.promo-box__text strong {
  display: block;
  font-size: 16px;
  margin-bottom: 4px;
}

.promo-box__text span {
  font-size: 13.5px;
  color: #b7bccb;
}

.promo-box__code {
  flex: none;
  display: inline-flex;
  align-items: center;
  gap: 10px;
  background: rgba(255, 255, 255, 0.08);
  border: 1px dashed rgba(255, 255, 255, 0.4);
  border-radius: var(--radius-md);
  padding: 10px 18px;
  font-size: 20px;
  font-weight: 800;
  letter-spacing: 0.06em;
  color: #fff;
}

/* ---------- Promo box: big CTA variant ---------- */

.promo-box--cta {
  flex-direction: column;
  align-items: stretch;
  text-align: center;
  padding: 36px 28px;
  margin: 28px 0 40px;
  background: linear-gradient(160deg, #1a2038 0%, var(--ink) 70%);
  box-shadow: var(--shadow);
}

.promo-box__title {
  font-size: 24px;
  font-weight: 800;
  letter-spacing: -0.01em;
  margin: 0 0 10px;
}

.promo-box__lead {
  font-size: 15px;
  color: #c3c8d6;
  max-width: 560px;
  margin: 0 auto 20px;
}

.promo-box__reasons {
  list-style: none;
  margin: 0 auto 26px;
  padding: 0;
  max-width: 480px;
  text-align: left;
  display: grid;
  gap: 10px;
}

.promo-box__reasons li {
  display: flex;
  gap: 10px;
  font-size: 14.5px;
  color: #dfe2ec;
}

.promo-box__reasons li::before {
  content: "✓";
  flex: none;
  color: #6ee7a8;
  font-weight: 800;
}

.promo-box__button {
  display: inline-flex;
  align-self: center;
  align-items: center;
  gap: 8px;
  background: var(--accent-gradient, var(--blue));
  color: #fff;
  font-weight: 700;
  font-size: 16px;
  text-decoration: none;
  padding: 15px 32px;
  border-radius: 999px;
  box-shadow: 0 10px 24px -8px rgba(77, 107, 255, 0.6);
  transition: transform 0.15s ease;
}

.promo-box__button:hover {
  transform: translateY(-1px);
}

/* ---------- Materials ---------- */

.materials {
  margin: 8px 0 28px;
}

.materials h2 {
  font-size: 18px;
  margin: 0 0 14px;
}

.materials-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
  gap: 12px;
}

.material-card {
  display: flex;
  align-items: center;
  gap: 12px;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: 14px 16px;
  text-decoration: none;
  color: var(--ink);
  transition: border-color 0.15s ease, transform 0.15s ease;
}

.material-card:hover {
  border-color: var(--blue);
  transform: translateY(-1px);
}

.material-card__icon {
  flex: none;
  width: 38px;
  height: 38px;
  border-radius: 10px;
  background: var(--blue-light);
  color: var(--blue);
  display: flex;
  align-items: center;
  justify-content: center;
}

.material-card__icon svg {
  width: 18px;
  height: 18px;
  fill: currentColor;
}

.material-card__text {
  min-width: 0;
}

.material-card__text strong {
  display: block;
  font-size: 14px;
  font-weight: 600;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.material-card__text span {
  font-size: 12.5px;
  color: var(--gray);
}

/* ---------- Lesson navigation ---------- */

.lesson-nav {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  margin: 28px 0 40px;
}

.lesson-nav__btn {
  display: flex;
  align-items: center;
  gap: 12px;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: 14px 18px;
  text-decoration: none;
  color: var(--ink);
  transition: border-color 0.15s ease, background 0.15s ease;
}

.lesson-nav__btn:hover {
  border-color: var(--blue);
  background: var(--blue-light);
}

.lesson-nav__btn.is-disabled {
  opacity: 0.4;
  pointer-events: none;
}

.lesson-nav__btn--next {
  justify-content: flex-end;
  text-align: right;
}

.lesson-nav__arrow {
  flex: none;
  width: 34px;
  height: 34px;
  border-radius: 50%;
  background: var(--blue);
  color: #fff;
  display: flex;
  align-items: center;
  justify-content: center;
}

.lesson-nav__arrow svg {
  width: 16px;
  height: 16px;
  fill: none;
  stroke: #fff;
  stroke-width: 2.4;
}

.lesson-nav__label {
  display: block;
  font-size: 11.5px;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--gray);
  margin-bottom: 2px;
}

.lesson-nav__title {
  display: block;
  font-size: 14.5px;
  font-weight: 700;
}

@media (max-width: 560px) {
  .lesson-nav {
    grid-template-columns: 1fr;
  }
  .lesson-nav__btn--next {
    justify-content: flex-start;
    text-align: left;
    flex-direction: row-reverse;
  }
}

/* Fixed side arrows for wide screens */

.side-arrow {
  position: fixed;
  top: 50%;
  transform: translateY(-50%);
  width: 46px;
  height: 46px;
  border-radius: 50%;
  background: var(--card);
  border: 1px solid var(--border);
  box-shadow: var(--shadow);
  display: flex;
  align-items: center;
  justify-content: center;
  text-decoration: none;
  color: var(--ink);
  z-index: 30;
  transition: background 0.15s ease, border-color 0.15s ease;
}

.side-arrow svg {
  width: 18px;
  height: 18px;
  fill: none;
  stroke: currentColor;
  stroke-width: 2.4;
}

.side-arrow:hover {
  background: var(--blue);
  border-color: var(--blue);
  color: #fff;
}

.side-arrow--prev {
  left: 22px;
}

.side-arrow--next {
  right: 22px;
}

.side-arrow.is-disabled {
  visibility: hidden;
}

@media (max-width: 1160px) {
  .side-arrow {
    display: none;
  }
}

/* ---------- Footer ---------- */

.site-footer {
  border-top: 1px solid var(--border);
  padding: 24px 0 40px;
  color: var(--gray);
  font-size: 12.5px;
  text-align: center;
}

.site-footer a {
  text-decoration: none;
  color: var(--gray);
}

.site-footer a:hover {
  color: var(--blue);
}

/* ---------- Lessons index page ---------- */

.index-hero {
  padding: 56px 0 24px;
  text-align: center;
}

.index-hero h1 {
  font-size: clamp(28px, 5vw, 42px);
  letter-spacing: -0.02em;
  margin: 12px 0;
}

.index-hero p {
  color: var(--ink-soft);
  font-size: 16px;
  max-width: 560px;
  margin: 0 auto;
}

.lessons-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 16px;
  margin: 32px 0 56px;
}

.lesson-card {
  display: block;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 20px;
  text-decoration: none;
  color: var(--ink);
  transition: transform 0.15s ease, border-color 0.15s ease;
}

.lesson-card:hover {
  transform: translateY(-2px);
  border-color: var(--blue);
}

.lesson-card__num {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 34px;
  height: 34px;
  border-radius: 10px;
  background: var(--blue-light);
  color: var(--blue);
  font-weight: 800;
  font-size: 14px;
  margin-bottom: 14px;
}

.lesson-card h3 {
  font-size: 16px;
  margin: 0 0 6px;
  letter-spacing: -0.01em;
}

.lesson-card p {
  font-size: 13.5px;
  color: var(--gray);
  margin: 0;
}