/* ---------- Design tokens ---------- */
:root {
  --color-primary: #00b6d1;
  --color-primary-dark: #009bb2;
  --color-success: #28a745;
  --color-success-dark: #218838;
  --color-dark: #1f2430;
  --color-dark-alt: #2a3040;
  --color-text: #222;
  --color-text-light: #555;
  --color-bg: #ffffff;
  --color-card-bg: #f9f9f9;
  --color-border: #e0e0e0;
  --color-white: #ffffff;

  --font-sans: "Segoe UI", system-ui, -apple-system, Arial, sans-serif;
  --radius-sm: 6px;
  --radius-md: 10px;
  --shadow-card: 0 4px 6px rgba(0, 0, 0, 0.1);
  --shadow-nav: 0 1px 3px rgba(0, 0, 0, 0.08);

  --container-max: 1160px;
}

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

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-sans);
  color: var(--color-text);
  background: var(--color-bg);
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
}

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

ul {
  list-style: none;
}

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

h1,
h2,
h3 {
  line-height: 1.2;
}

button {
  font-family: inherit;
}

:focus-visible {
  outline: 3px solid var(--color-primary);
  outline-offset: 2px;
  border-radius: 3px;
}

/* ---------- Accessibility helpers ---------- */
.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  margin: -1px;
  padding: 0;
  overflow: hidden;
  clip: rect(0 0 0 0);
  white-space: nowrap;
  border: 0;
}

.skip-link {
  position: absolute;
  top: -100px;
  left: 0;
  z-index: 200;
  background: var(--color-dark);
  color: var(--color-white);
  padding: 0.7rem 1.2rem;
  border-radius: 0 0 var(--radius-sm) 0;
  transition: top 0.15s ease;
}

.skip-link:focus {
  top: 0;
}

/* ---------- Demo notice ---------- */
.demo-banner {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.6rem;
  flex-wrap: wrap;
  text-align: center;
  background: #fff3cd;
  color: #664d03;
  border-bottom: 1px solid #ffe69c;
  padding: 0.55rem clamp(1rem, 4vw, 3rem);
  font-size: 0.88rem;
}

.demo-banner svg {
  width: 18px;
  height: 18px;
  flex-shrink: 0;
}

.demo-banner p {
  margin: 0;
}

/* ---------- Brand ---------- */
.brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
}

.brand-mark {
  width: 30px;
  height: 30px;
  color: var(--color-primary);
  flex-shrink: 0;
}

.brand-name {
  font-size: 1.3rem;
  font-weight: 700;
  letter-spacing: 0.02em;
}

/* ---------- Navbar ---------- */
.navbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  padding: 0.9rem clamp(1rem, 4vw, 3rem);
  max-width: var(--container-max);
  margin: 0 auto;
  box-shadow: var(--shadow-nav);
  position: sticky;
  top: 0;
  background: var(--color-bg);
  z-index: 100;
}

.nav-menu {
  display: flex;
  align-items: center;
  gap: 1.6rem;
}

.nav-menu a {
  font-size: 0.95rem;
  color: var(--color-text);
  transition: color 0.15s ease;
}

.nav-menu a:hover {
  color: var(--color-primary);
}

.nav-tools {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  margin-left: 0.5rem;
}

.icon-btn {
  display: inline-flex;
  background: none;
  border: none;
  cursor: pointer;
  padding: 4px;
}

.icon-btn svg {
  width: 20px;
  height: 20px;
  color: var(--color-text-light);
  transition: color 0.15s ease;
}

.icon-btn:hover svg {
  color: var(--color-primary);
}

.search-form {
  display: none;
  align-items: center;
}

.search-form.open {
  display: inline-flex;
}

.search-form input {
  width: 190px;
  padding: 0.45rem 0.7rem;
  font-size: 0.9rem;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  background: var(--color-card-bg);
  color: var(--color-text);
}

.nav-toggle {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  padding: 4px;
}

.nav-toggle svg {
  width: 26px;
  height: 26px;
  color: var(--color-text);
}

/* ---------- Hero ---------- */
.hero {
  text-align: center;
  padding: clamp(3rem, 8vw, 5.5rem) clamp(1rem, 4vw, 3rem) 2rem;
  max-width: var(--container-max);
  margin: 0 auto;
}

.hero h1 {
  font-size: clamp(2rem, 5vw, 3.2rem);
  font-weight: 400;
  margin-bottom: 1.2rem;
}

.hero h1 strong {
  font-weight: 700;
}

.hero-sub {
  max-width: 640px;
  margin: 0 auto 1.8rem;
  color: var(--color-text-light);
  font-size: 1.05rem;
}

.hero-cta {
  display: flex;
  justify-content: center;
  flex-wrap: wrap;
  gap: 0.8rem;
  margin-bottom: 2.4rem;
}

.version-badge {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  justify-content: center;
  flex-wrap: wrap;
  margin-top: 0.5rem;
}

.version-badge p {
  color: var(--color-text-light);
  font-size: 0.95rem;
}

.version-badge a {
  color: var(--color-primary);
}

.version-badge a:hover {
  text-decoration: underline;
}

/* ---------- Buttons ---------- */
.btn {
  display: inline-block;
  padding: 0.75rem 1.5rem;
  border-radius: var(--radius-sm);
  font-size: 0.9rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  border: 2px solid transparent;
  cursor: pointer;
  transition: background-color 0.2s ease, color 0.2s ease, border-color 0.2s ease;
}

.btn-primary {
  background: var(--color-primary);
  color: var(--color-white);
}

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

.btn-ghost {
  background: transparent;
  color: var(--color-primary);
  border-color: var(--color-primary);
}

.btn-ghost:hover {
  background: var(--color-primary);
  color: var(--color-white);
}

.download-btn {
  display: inline-block;
  margin-top: 0.8rem;
  padding: 0.6rem 1.4rem;
  background: var(--color-success);
  color: var(--color-white);
  border-radius: var(--radius-sm);
  font-weight: 700;
  font-size: 0.9rem;
  transition: background-color 0.2s ease;
}

.download-btn:hover {
  background: var(--color-success-dark);
}

/* ---------- Sections ---------- */
.section-title {
  font-size: clamp(1.6rem, 3vw, 2.2rem);
  text-align: center;
  margin-bottom: 0.4rem;
}

.section-sub {
  text-align: center;
  color: var(--color-text-light);
  margin-bottom: 2rem;
}

/* ---------- Download cards ---------- */
.cards {
  padding: 1rem clamp(1rem, 4vw, 3rem) 3rem;
  max-width: var(--container-max);
  margin: 0 auto;
}

.download-lang {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 1.25rem;
}

.download-box {
  background: var(--color-card-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 1.5rem 1.25rem;
  text-align: center;
  box-shadow: var(--shadow-card);
  display: flex;
  flex-direction: column;
  align-items: center;
}

.download-box h3 {
  font-size: 1.15rem;
  margin-bottom: 0.3rem;
}

.checksum {
  margin-top: 1rem;
  font-size: 0.66rem;
  color: var(--color-text-light);
  word-break: break-all;
  line-height: 1.4;
}

.copy-btn {
  margin-top: 0.7rem;
  background: none;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  padding: 0.35rem 0.9rem;
  font-size: 0.78rem;
  cursor: pointer;
  color: var(--color-text-light);
  transition: color 0.15s ease, border-color 0.15s ease, background-color 0.15s ease;
}

.copy-btn:hover {
  color: var(--color-primary);
  border-color: var(--color-primary);
}

.copy-btn.copied {
  background: var(--color-success);
  border-color: var(--color-success);
  color: var(--color-white);
}

/* ---------- OS tabs ---------- */
.tabs {
  display: flex;
  justify-content: center;
  gap: 0.5rem;
  margin-bottom: 1.5rem;
}

.tab {
  background: var(--color-card-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  padding: 0.5rem 1.3rem;
  font-size: 0.9rem;
  font-weight: 600;
  cursor: pointer;
  color: var(--color-text-light);
  transition: color 0.15s ease, border-color 0.15s ease, background-color 0.15s ease;
}

.tab:hover {
  color: var(--color-primary);
  border-color: var(--color-primary);
}

.tab.active {
  background: var(--color-primary);
  border-color: var(--color-primary);
  color: var(--color-white);
}

.sr-status:empty {
  display: none;
}

/* ---------- Newsletter (dark) ---------- */
.newsletter {
  background: var(--color-dark);
  color: var(--color-white);
  padding: clamp(2.5rem, 6vw, 4rem) clamp(1rem, 4vw, 3rem);
}

.newsletter-grid {
  max-width: var(--container-max);
  margin: 0 auto;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: clamp(2rem, 5vw, 4rem);
  align-items: start;
}

.newsletter-copy h2 {
  font-size: clamp(1.4rem, 3vw, 1.9rem);
  margin-bottom: 0.8rem;
}

.newsletter-copy > p {
  color: #c6cbd6;
  max-width: 480px;
}

.newsletter-card {
  background: var(--color-white);
  color: var(--color-text);
  border-radius: var(--radius-md);
  padding: 1.5rem;
  margin-top: 1.5rem;
  max-width: 360px;
  text-align: center;
}

.card-title {
  font-weight: 600;
  color: var(--color-primary);
  margin-bottom: 1rem;
}

.newsletter-card form {
  text-align: left;
}

.newsletter-card label {
  display: block;
  font-size: 0.85rem;
  color: var(--color-text);
  margin-bottom: 0.4rem;
}

.newsletter-card input[type="email"] {
  width: 100%;
  padding: 0.7rem 0.8rem;
  font-size: 0.95rem;
  border: 1px solid rgba(51, 51, 51, 0.16);
  border-radius: var(--radius-sm);
  margin-bottom: 0.8rem;
  background: var(--color-white);
}

.newsletter-card .btn {
  width: 100%;
}

.form-status {
  min-height: 1.2rem;
  margin-top: 0.6rem;
  font-size: 0.85rem;
  text-align: center;
}

.form-status.ok {
  color: var(--color-success);
}

.form-status.err {
  color: #d9534f;
}

.newsletter-info h3 {
  font-size: 1.15rem;
  margin: 0 0 0.5rem;
}

.newsletter-info h3 + p {
  color: #c6cbd6;
  margin-bottom: 1.6rem;
}

.newsletter-info a {
  color: var(--color-primary);
}

.newsletter-info a:hover {
  text-decoration: underline;
}

/* ---------- Features ---------- */
.features {
  padding: clamp(2.5rem, 6vw, 4rem) clamp(1rem, 4vw, 3rem);
  max-width: var(--container-max);
  margin: 0 auto;
}

.feature-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 1.25rem;
}

.feature {
  background: var(--color-card-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 1.5rem;
}

.feature h3 {
  margin-bottom: 0.4rem;
  font-size: 1.1rem;
}

.feature p {
  color: var(--color-text-light);
  font-size: 0.95rem;
}

/* ---------- Pricing ---------- */
.pricing {
  padding: clamp(2.5rem, 6vw, 4rem) clamp(1rem, 4vw, 3rem);
  max-width: var(--container-max);
  margin: 0 auto;
}

.pricing-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: 1.25rem;
  align-items: stretch;
}

.price-card {
  background: var(--color-card-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 1.75rem 1.5rem;
  text-align: center;
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.price-card.featured {
  border: 2px solid var(--color-primary);
  box-shadow: var(--shadow-card);
  position: relative;
}

.price-card.featured::before {
  content: "Most popular";
  position: absolute;
  top: -0.85rem;
  left: 50%;
  transform: translateX(-50%);
  background: var(--color-primary);
  color: var(--color-white);
  font-size: 0.72rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  padding: 0.25rem 0.9rem;
  border-radius: 999px;
}

.price-card h3 {
  font-size: 1.15rem;
}

.price-card .price {
  font-size: 2.4rem;
  font-weight: 700;
}

.price-card .price span {
  font-size: 0.95rem;
  font-weight: 400;
  color: var(--color-text-light);
}

.price-card ul {
  list-style: none;
  margin: 0;
  padding: 0;
  color: var(--color-text-light);
  font-size: 0.92rem;
  flex-grow: 1;
}

.price-card ul li {
  padding: 0.35rem 0;
}

/* ---------- Changelog ---------- */
.changelog {
  padding: clamp(2.5rem, 6vw, 4rem) clamp(1rem, 4vw, 3rem);
  max-width: var(--container-max);
  margin: 0 auto;
}

.changelog-list {
  max-width: 640px;
  margin: 0 auto;
}

.changelog-list article {
  padding: 1.1rem 0;
  border-bottom: 1px solid var(--color-border);
}

.changelog-list article:first-of-type {
  border-top: 1px solid var(--color-border);
}

.changelog-list h3 {
  font-size: 1rem;
  margin-bottom: 0.4rem;
}

.changelog-list ul {
  list-style: none;
  margin: 0;
  padding: 0;
  color: var(--color-text-light);
  font-size: 0.92rem;
}

/* ---------- Contact ---------- */
.contact {
  padding: clamp(2.5rem, 6vw, 4rem) clamp(1rem, 4vw, 3rem);
  max-width: var(--container-max);
  margin: 0 auto;
}

.contact-card {
  max-width: 560px;
  margin: 0 auto;
  background: var(--color-card-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 1.5rem;
  text-align: center;
  color: var(--color-text-light);
  display: grid;
  gap: 0.6rem;
}

.contact-card a {
  color: var(--color-primary);
  font-weight: 600;
}

.contact-card a:hover {
  text-decoration: underline;
}

/* ---------- Footer ---------- */
footer {
  background: var(--color-dark-alt);
  color: var(--color-white);
  padding: clamp(2rem, 5vw, 3.5rem) clamp(1rem, 4vw, 3rem) 1.5rem;
}

.footer-columns {
  max-width: var(--container-max);
  margin: 0 auto;
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 2rem;
  margin-bottom: 2.5rem;
}

.foot-col h3 {
  font-size: 1.05rem;
  margin-bottom: 0.9rem;
}

.foot-col ul li {
  color: #c6cbd6;
  font-size: 0.9rem;
  padding: 0.22rem 0;
}

.foot-col ul a:hover {
  color: var(--color-primary);
}

.foot-newsletter p {
  color: #c6cbd6;
  font-size: 0.9rem;
  margin-bottom: 0.8rem;
}

.subscribe-form input[type="email"] {
  width: 100%;
  padding: 0.6rem 0.8rem;
  font-size: 0.9rem;
  border: none;
  border-radius: var(--radius-sm);
  margin-bottom: 0.6rem;
  background: var(--color-bg);
}

.subscribe-form .btn {
  width: 100%;
}

.footer-bottom {
  max-width: var(--container-max);
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 1rem;
  padding-top: 1.5rem;
  border-top: 1px solid rgba(255, 255, 255, 0.12);
}

.footer-bottom .brand {
  color: var(--color-white);
}

.social {
  display: flex;
  align-items: center;
  gap: 0.8rem;
}

.social svg {
  width: 26px;
  height: 26px;
  color: #c6cbd6;
  transition: color 0.15s ease;
}

.social a:hover svg {
  color: var(--color-primary);
}

.copyright {
  max-width: var(--container-max);
  margin: 1.2rem auto 0;
  color: #8a93a6;
  font-size: 0.85rem;
  text-align: center;
}

/* ---------- Back to top ---------- */
.to-top {
  position: fixed;
  right: 1.25rem;
  bottom: 1.25rem;
  z-index: 90;
  width: 44px;
  height: 44px;
  border-radius: 50%;
  border: none;
  background: var(--color-primary);
  color: var(--color-white);
  cursor: pointer;
  display: grid;
  place-items: center;
  opacity: 0;
  visibility: hidden;
  transform: translateY(10px);
  transition: opacity 0.2s ease, transform 0.2s ease, visibility 0.2s ease;
  box-shadow: var(--shadow-card);
}

.to-top.visible {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.to-top:hover {
  background: var(--color-primary-dark);
}

.to-top svg {
  width: 22px;
  height: 22px;
}

/* ---------- 404 page ---------- */
.error-body {
  display: flex;
  flex-direction: column;
  min-height: 100vh;
}

.error-body .navbar {
  box-shadow: none;
}

.error-main {
  flex: 1;
  display: grid;
  place-content: center;
  text-align: center;
  gap: 0.8rem;
  padding: 2rem 1rem;
  max-width: var(--container-max);
  margin: 0 auto;
}

.error-code {
  font-size: clamp(5rem, 20vw, 9rem);
  font-weight: 800;
  color: var(--color-primary);
  line-height: 1;
}

.error-main h1 {
  font-size: clamp(1.5rem, 4vw, 2.2rem);
}

.error-main p {
  color: var(--color-text-light);
}

.error-main .btn {
  justify-self: center;
  margin-top: 0.8rem;
}

/* ---------- Responsive ---------- */
@media (max-width: 900px) {
  .newsletter-grid {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 768px) {
  .nav-toggle {
    display: block;
  }

  .nav-menu {
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    background: var(--color-bg);
    box-shadow: var(--shadow-card);
    padding: 0.5rem 0;
    transform: scaleY(0);
    transform-origin: top;
    transition: transform 0.18s ease;
  }

  .nav-menu.open {
    transform: scaleY(1);
  }

  .nav-menu li {
    border-bottom: 1px solid var(--color-border);
  }

  .nav-menu li:last-child {
    border-bottom: none;
  }

  .nav-menu a {
    display: block;
    padding: 0.85rem clamp(1rem, 4vw, 3rem);
  }

  .nav-tools {
    margin-left: 0;
    gap: 0.8rem;
    padding: 0.6rem clamp(1rem, 4vw, 3rem);
  }

  .search-form.open {
    display: flex;
    flex: 1;
  }

  .search-form input {
    width: 100%;
  }
}

@media (max-width: 480px) {
  .hero-cta .btn {
    width: 100%;
    max-width: 340px;
  }
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }

  *,
  *::before,
  *::after {
    transition: none !important;
  }
}