/* ============================================================================
   ML Engineer Mentorship — стили лендинга.
   Опираются на токены ChatGPT-темы (design/chatgpt-theme.css):
   var(--color-surface), --color-text, --radius-*, --font-* и т. д.
   ============================================================================ */

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: var(--font-sans);
  font: 400 var(--font-text-md);
  background-color: var(--color-surface);
  color: var(--color-text);
}

a { color: inherit; text-decoration: none; }

.container {
  width: 100%;
  max-width: 920px;
  margin-inline: auto;
  padding-inline: 24px;
}

.muted { color: var(--color-text-tertiary); }

/* ------------------------------- Кнопки ---------------------------------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  border: 1px solid transparent;
  border-radius: var(--radius-full);
  padding: 9px 18px;
  font: 500 var(--font-text-sm);
  cursor: pointer;
  transition: background-color var(--transition-duration-basic) ease,
              border-color var(--transition-duration-basic) ease,
              opacity var(--transition-duration-basic) ease;
  white-space: nowrap;
}
.btn-lg { padding: 13px 26px; font-size: 1rem; }

.btn-primary {
  background-color: var(--color-primary-bg);
  color: var(--color-primary-text);
}
.btn-primary:hover { background-color: var(--color-primary-bg-hover); }

.btn-outline {
  border-color: var(--color-border-strong);
  color: var(--color-text);
  background-color: transparent;
}
.btn-outline:hover { background-color: var(--color-surface-secondary); }

.btn-ghost {
  background: transparent;
  color: var(--color-text);
  padding: 8px 10px;
  font-size: 1rem;
}
.btn-ghost:hover { background-color: var(--color-surface-secondary); }

/* ------------------------------- Шапка ----------------------------------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 10;
  background-color: color-mix(in srgb, var(--color-surface) 85%, transparent);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--color-border-subtle);
}
.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 60px;
}
.brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  font: 600 var(--font-heading-xs);
}
.brand-mark {
  width: 47px;
  height: 47px;
  flex: none;
  color: var(--color-text);
}
.header-nav {
  display: flex;
  align-items: center;
  gap: 18px;
}
.header-nav > a:not(.btn) {
  font-size: 0.875rem;
  color: var(--color-text-secondary);
}
.header-nav > a:not(.btn):hover { color: var(--color-text); }

/* -------------------------------- HERO ----------------------------------- */
.hero {
  padding-block: 96px 64px;
  text-align: center;
}
.hero h1 {
  margin: 0 0 20px;
  font: 600 var(--font-heading-3xl);
  letter-spacing: -0.02em;
}
.hero-sub {
  max-width: 640px;
  margin: 0 auto 32px;
  font: 400 var(--font-text-lg);
  color: var(--color-text-secondary);
}
.hero-actions {
  display: flex;
  gap: 12px;
  justify-content: center;
  flex-wrap: wrap;
}

/* ------------------------------- Секции ---------------------------------- */
.section { padding-block: 56px; }
.section-title {
  margin: 0 0 8px;
  font: 600 var(--font-heading-lg);
}
.section-lead {
  margin: 0 0 32px;
  color: var(--color-text-secondary);
  max-width: 640px;
}

/* --------------------------- Сетка программы ----------------------------- */
.course-grid {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 12px;
}
.course-card {
  display: flex;
  align-items: center;
  gap: 16px;
  width: 100%;
  text-align: left;
  padding: 18px 20px;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-2xl);
  background-color: var(--color-surface);
  color: inherit;
  font: inherit;
  cursor: pointer;
  transition: background-color var(--transition-duration-basic) ease,
              border-color var(--transition-duration-basic) ease,
              transform var(--transition-duration-basic) ease;
}
.course-card:hover {
  background-color: var(--color-surface-secondary);
  border-color: var(--color-border-strong);
  transform: translateY(-1px);
}
.course-num {
  font: 600 var(--font-heading-md);
  color: var(--color-text-tertiary);
  font-variant-numeric: tabular-nums;
}
.course-name { font-weight: 500; }
.course-arrow {
  margin-left: auto;
  color: var(--color-text-tertiary);
  opacity: 0;
  transform: translateX(-4px);
  transition: opacity var(--transition-duration-basic) ease,
              transform var(--transition-duration-basic) ease;
}
.course-card:hover .course-arrow { opacity: 1; transform: translateX(0); }

/* ----------------------- Модальное окно раздела -------------------------- */
.section-dialog {
  width: min(560px, calc(100vw - 32px));
  border: 1px solid var(--color-border);
  border-radius: var(--radius-3xl);
  background-color: var(--color-surface-elevated);
  color: var(--color-text);
  padding: 28px;
  box-shadow: var(--shadow-400);
}
.section-dialog::backdrop {
  background: rgb(0 0 0 / 45%);
  backdrop-filter: blur(2px);
}
.dialog-head {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 16px;
}
.dialog-num {
  font: 600 var(--font-text-sm);
  color: var(--color-text-tertiary);
  font-variant-numeric: tabular-nums;
}
.dialog-title { margin: 2px 0 0; font: 600 var(--font-heading-md); }
.dialog-close { flex: none; }
.dialog-desc {
  margin: 12px 0 0;
  color: var(--color-text-secondary);
  font-size: 0.9375rem;
  line-height: 1.5;
}
.dialog-subhead {
  margin: 22px 0 10px;
  font: 600 var(--font-text-sm);
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: var(--color-text-tertiary);
}
.dialog-topics { margin: 0; padding-left: 0; list-style: none; display: grid; gap: 8px; }
.dialog-topics li {
  position: relative;
  padding-left: 24px;
  font-size: 0.9375rem;
  line-height: 1.45;
}
.dialog-topics li::before {
  content: "";
  position: absolute;
  left: 6px;
  top: 0.55em;
  width: 6px;
  height: 6px;
  border-radius: var(--radius-full);
  background: var(--green-500);
}
.dialog-note {
  margin: 22px 0 0;
  padding-top: 16px;
  border-top: 1px solid var(--color-border-subtle);
  font-size: 0.8125rem;
  color: var(--color-text-tertiary);
}

/* ----------------------- Причины взять менторство ------------------------ */
.reasons-grid {
  list-style: none;
  margin: 0;
  padding: 0;
  counter-reset: none;
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 12px;
}
.reason {
  display: flex;
  align-items: flex-start;
  gap: 16px;
  padding: 22px 22px;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-2xl);
  background-color: var(--color-surface);
}
.reason-num {
  flex: none;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 34px;
  height: 34px;
  border-radius: var(--radius-full);
  background-color: var(--color-surface-secondary);
  color: var(--green-600);
  font: 600 var(--font-text-md);
  font-variant-numeric: tabular-nums;
}
.reason-text {
  margin: 4px 0 0;
  font-size: 0.9375rem;
  line-height: 1.55;
  color: var(--color-text-secondary);
}

/* --------------------------- Мой путь в ML ------------------------------- */
.prose {
  max-width: 760px;
}
.prose p {
  margin: 0 0 18px;
  font: 400 var(--font-text-lg);
  line-height: 1.65;
  color: var(--color-text-secondary);
}
.prose p:last-child { margin-bottom: 0; }

.subsection-title {
  margin: 40px 0 16px;
  font: 600 var(--font-heading-sm);
}
.facts-list {
  margin: 0;
  padding: 0;
  list-style: none;
  display: grid;
  gap: 12px;
  max-width: 760px;
}
.facts-list li {
  position: relative;
  padding-left: 24px;
  font-size: 0.9375rem;
  line-height: 1.55;
  color: var(--color-text-secondary);
}
.facts-list li::before {
  content: "";
  position: absolute;
  left: 6px;
  top: 0.6em;
  width: 6px;
  height: 6px;
  border-radius: var(--radius-full);
  background: var(--green-500);
}
.facts-list strong { color: var(--color-text); }
.path-cta { margin-top: 36px; }

/* ----------------------------- Об авторе --------------------------------- */
.author-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 16px;
}
.card {
  border: 1px solid var(--color-border);
  border-radius: var(--radius-3xl);
  background-color: var(--color-surface);
  padding: 24px;
}
.card-title {
  margin: 0 0 16px;
  font: 600 var(--font-heading-sm);
}

.timeline { list-style: none; margin: 0; padding: 0; display: grid; gap: 18px; }
.tl-head {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  gap: 12px;
}
.tl-role { font-weight: 600; }
.tl-meta { color: var(--color-text-tertiary); font-size: 0.8125rem; white-space: nowrap; }
.tl-org { color: var(--color-text-secondary); font-size: 0.875rem; margin-top: 2px; }
.tl-desc { margin: 6px 0 0; font-size: 0.875rem; color: var(--color-text-secondary); line-height: 1.5; }

.plain-list { margin: 0; padding-left: 0; list-style: none; display: grid; gap: 14px; }
.plain-list li { font-size: 0.9375rem; line-height: 1.5; }
.plain-list a:hover { color: var(--green-600); }

.chip-list { list-style: none; margin: 0; padding: 0; display: flex; flex-wrap: wrap; gap: 8px; }
.chip {
  border: 1px solid var(--color-border);
  border-radius: var(--radius-full);
  padding: 6px 12px;
  font-size: 0.8125rem;
  background-color: var(--color-surface-secondary);
}
.chip .muted { margin-left: 4px; }

/* ------------------------------- Подвал ---------------------------------- */
.site-footer {
  border-top: 1px solid var(--color-border-subtle);
  padding-block: 28px;
  margin-top: 32px;
}
.site-footer .container {
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 0.875rem;
}

/* ----------------------------- Адаптив ----------------------------------- */
@media (max-width: 640px) {
  .hero { padding-block: 64px 48px; }
  .hero h1 { font-size: 2.25rem; line-height: 2.5rem; }
  .course-grid,
  .reasons-grid,
  .author-grid { grid-template-columns: 1fr; }
  .header-nav > a:not(.btn) { display: none; }
}