/* ===== Глобальные стили и CSS-переменные ===== */
:root {
  /* Цвета — светлая тема */
  --color-bg: #f8fafc;
  --color-bg-alt: #ffffff;
  --color-text: #0f172a;
  --color-text-secondary: #475569;
  --color-accent: #4F46E5;
  --color-accent-hover: #4338CA;
  --color-border: #e2e8f0;
  --color-card-bg: #ffffff;
  --color-footer-bg: #1e293b;
  --color-footer-text: #cbd5e1;

  /* Типографика */
  --font-main: 'Segoe UI', 'Arial', sans-serif;
  --font-heading: 'Segoe UI', 'Arial', sans-serif;
  --font-mono: 'Courier New', monospace;

  /* Размеры */
  --header-height: 64px;
  --max-width: 1200px;
  --border-radius: 12px;
  --border-radius-sm: 8px;
}

/* Тёмная тема */
html.dark {
  --color-bg: #0f172a;
  --color-bg-alt: #1e293b;
  --color-text: #e2e8f0;
  --color-text-secondary: #94a3b8;
  --color-accent: #818cf8;
  --color-accent-hover: #6366f1;
  --color-border: #334155;
  --color-card-bg: #1e293b;
  --color-footer-bg: #020617;
  --color-footer-text: #94a3b8;
}

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

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

body {
  font-family: var(--font-main);
  background-color: var(--color-bg);
  color: var(--color-text);
  line-height: 1.6;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  transition: background-color 0.3s, color 0.3s;
}

a {
  color: var(--color-accent);
  text-decoration: none;
  transition: color 0.2s;
}

a:hover {
  color: var(--color-accent-hover);
}

img {
  max-width: 100%;
  height: auto;
  display: block;
}

ul, ol {
  list-style: none;
}

button {
  font-family: var(--font-main);
  cursor: pointer;
  border: none;
  transition: all 0.2s;
}

/* Фокус через клавиатуру (доступность) */
:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: 2px;
}

button:focus-visible,
a:focus-visible,
input:focus-visible,
textarea:focus-visible,
select:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: 2px;
}

/* Контейнер */
.container {
  width: 100%;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 20px;
}

/* ===== Шапка ===== */
.header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: var(--header-height);
  background-color: var(--color-bg-alt);
  border-bottom: 1px solid var(--color-border);
  z-index: 1000;
  transition: background-color 0.3s, border-color 0.3s;
}

.header__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 100%;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 20px;
}

.header__logo {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--color-text);
}

.header__logo svg {
  width: 32px;
  height: 32px;
}

/* Навигация */
.nav {
  display: flex;
  align-items: center;
  gap: 32px;
}

.nav__link {
  font-size: 0.95rem;
  font-weight: 500;
  color: var(--color-text-secondary);
  position: relative;
  padding: 4px 0;
}

.nav__link::after {
  content: '';
  position: absolute;
  bottom: -2px;
  left: 0;
  width: 0;
  height: 2px;
  background-color: var(--color-accent);
  transition: width 0.3s;
}

.nav__link:hover::after,
.nav__link.active::after {
  width: 100%;
}

.nav__link.active {
  color: var(--color-accent);
}

/* Кнопка темы */
.theme-toggle {
  width: 40px;
  height: 40px;
  border-radius: 50%;
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.2rem;
  color: var(--color-text);
  transition: background-color 0.3s, border-color 0.3s;
  flex-shrink: 0;
}

.theme-toggle:hover {
  background: var(--color-accent);
  color: #fff;
  border-color: var(--color-accent);
}

/* Бургер */
.burger {
  display: none;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  width: 40px;
  height: 40px;
  background: none;
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius-sm);
  cursor: pointer;
  padding: 8px;
  gap: 5px;
}

.burger__line {
  display: block;
  width: 100%;
  height: 2px;
  background: var(--color-text);
  border-radius: 2px;
  transition: transform 0.3s, opacity 0.3s;
}

.burger.active .burger__line:nth-child(1) {
  transform: translateY(7px) rotate(45deg);
}

.burger.active .burger__line:nth-child(2) {
  opacity: 0;
}

.burger.active .burger__line:nth-child(3) {
  transform: translateY(-7px) rotate(-45deg);
}

/* ===== Подвал ===== */
.footer {
  margin-top: auto;
  background-color: var(--color-footer-bg);
  color: var(--color-footer-text);
  padding: 40px 0 20px;
}

.footer__inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 20px;
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  align-items: center;
  gap: 20px;
}

.footer__copy {
  font-size: 0.9rem;
}

.footer__links {
  display: flex;
  gap: 24px;
  align-items: center;
}

.footer__link {
  color: var(--color-footer-text);
  font-size: 0.9rem;
}

.footer__link:hover {
  color: #fff;
}

.footer__up {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 10px 18px;
  border-radius: var(--border-radius-sm);
  background: var(--color-accent);
  color: #fff;
  font-size: 0.9rem;
  font-weight: 500;
}

.footer__up:hover {
  background: var(--color-accent-hover);
  color: #fff;
}

/* ===== Адаптив для шапки ===== */
/* Mobile (< 768px) */
@media (max-width: 767px) {
  .nav {
    position: fixed;
    top: var(--header-height);
    left: 0;
    right: 0;
    background: var(--color-bg-alt);
    flex-direction: column;
    padding: 20px;
    gap: 16px;
    border-bottom: 1px solid var(--color-border);
    transform: translateY(-100%);
    opacity: 0;
    pointer-events: none;
    transition: transform 0.3s, opacity 0.3s;
  }

  .nav.open {
    transform: translateY(0);
    opacity: 1;
    pointer-events: auto;
  }

  .burger {
    display: flex;
  }

  .header__controls {
    display: flex;
    align-items: center;
    gap: 12px;
  }
}

/* Footer mobile */
@media (max-width: 767px) {
  .footer__inner {
    flex-direction: column;
    text-align: center;
  }

  .footer__links {
    flex-wrap: wrap;
    justify-content: center;
  }
}

/* Tablet (768px–1199px) */
@media (min-width: 768px) and (max-width: 1199px) {
  .header__inner {
    padding: 0 32px;
  }
}

/* Desktop (>= 1200px) */
@media (min-width: 1200px) {
  .header__inner {
    padding: 0 20px;
  }
}