*,
*::before,
*::after {
  box-sizing: border-box;
}

:root {
  --bg: oklch(0.18 0.02 280);
  --surface: oklch(0.25 0.03 280);
  --surface-2: oklch(0.32 0.04 280);
  --text: oklch(0.95 0.01 90);
  --text-muted: oklch(0.75 0.02 90);
  --accent: oklch(0.75 0.25 335);
  --accent-hover: oklch(0.82 0.22 335);
  --accent-soft: oklch(0.75 0.25 335 / 0.15);
  --error: oklch(0.65 0.2 25);
  --success: oklch(0.7 0.15 145);
  --border: oklch(0.4 0.03 280);
  --font: "Segoe UI", "Helvetica Neue", Arial, sans-serif;
  --line-height-body: 1.6;
  --line-height-heading: 1.2;
  --xs: 0.25rem;
  --sm: 0.5rem;
  --md: 1rem;
  --lg: 1.5rem;
  --xl: 2.5rem;
  --xxl: 4rem;
  --container: 70rem;
  --radius: 0.5rem;
  --shadow: 0 0.5rem 1.5rem oklch(0 0 0 / 0.35);
  --transition: 0.25s ease;
}

body {
  margin: 0;
  padding: 0;
  font-family: var(--font);
  font-size: 1rem;
  line-height: var(--line-height-body);
  color: var(--text);
  background-color: var(--bg);
}

.container {
  width: min(100% - 2rem, var(--container));
  margin-inline: auto;
}

h1, h2, h3, h4 {
  font-family: var(--font);
  line-height: var(--line-height-heading);
  margin-block: 0 0.6em;
  color: var(--text);
}

h1 { font-size: clamp(1.8rem, 5vw, 2.8rem); }
h2 { font-size: clamp(1.4rem, 3.5vw, 2rem); }
h3 { font-size: clamp(1.2rem, 2.5vw, 1.5rem); }

p {
  margin-block: 0 1em;
  color: var(--text-muted);
}

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

  &:hover,
  &:focus-visible {
    color: var(--accent-hover);
  }
}

img {
  max-inline-size: 100%;
  block-size: auto;
  display: block;
}

header {
  background-color: var(--surface);
  border-block-end: 1px solid var(--border);
  position: sticky;
  inset-block-start: 0;
  z-index: 100;
  padding-block: var(--md);
}

.header-inner {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: var(--md);
}

.logo {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--accent);
  letter-spacing: 0.02em;

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

.nav-toggle {
  display: block;
  background: none;
  border: 1px solid var(--border);
  color: var(--text);
  padding: 0.4rem 0.7rem;
  border-radius: var(--radius);
  cursor: pointer;
  font-size: 1.1rem;
}

.main-nav {
  display: none;
  flex-direction: column;
  gap: var(--sm);
  width: 100%;
  padding-top: var(--md);

  &.is-open {
    display: flex;
  }

  a {
    color: var(--text);
    padding: 0.5rem 0.75rem;
    border-radius: var(--radius);

    &:hover,
    &[aria-current="page"] {
      background-color: var(--accent-soft);
      color: var(--accent);
    }
  }
}
.home {
  position: relative;
  padding-block: var(--xxl);
  text-align: center;
  background: linear-gradient(oklch(0.18 0.04 280), oklch(0.12 0.03 280));
  border-block-end: 1px solid var(--border);

  h1 {
    color: var(--accent);
    margin-block-end: var(--md);
  }

  p {
    font-size: 1.15rem;
    color: var(--text);
  }
}

.home__content {
  max-inline-size: 40rem;
  margin-inline: auto;
}

.card {
  position: relative;
  background-color: var(--surface);
  border-radius: var(--radius);
  overflow: hidden;
  border: 1px solid var(--border);
  transition: transform var(--transition), box-shadow var(--transition);

  & h3 {
    margin-block-end: 0.4em;
  }

  &:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow);
  }
}

.card__link {
  position: absolute;
  inset: 0;
  z-index: 1;
}

.card__body {
  padding: var(--lg);
  position: relative;
  z-index: 0;
}

section {
  padding-block: var(--xxl);
}

.section--alt {
  background-color: var(--surface-2);
}

.section__title {
  text-align: center;
  margin-block-end: var(--xl);
  color: var(--accent);
}

.flex-row {
  display: flex;
  flex-direction: column;
  gap: var(--lg);
}

.grid-cards {
  display: flex;
  flex-direction: column;
  gap: var(--lg);
}

.form-group {
  margin-block-end: var(--lg);

  label {
    display: block;
    font-weight: 600;
    margin-block-end: var(--xs);
    color: var(--text);
  }

  input,
  textarea,
  select {
    width: 100%;
    padding: 0.75rem 1rem;
    border: 1px solid var(--border);
    border-radius: var(--radius);
    background-color: var(--surface-2);
    color: var(--text);
    font: inherit;
    transition: border-color var(--transition);

    &:focus {
      outline: 2px solid var(--accent);
      outline-offset: 2px;
      border-color: var(--accent);
    }
  }

  textarea {
    min-block-size: 8rem;
    resize: vertical;
  }

  input[type="checkbox"],
  input[type="radio"] {
    width: auto;
    margin: 0;
    flex-shrink: 0;
  }

  label:has(> input[type="checkbox"]),
  label:has(> input[type="radio"]) {
    display: flex;
    align-items: center;
    gap: 0.6rem;
    font-weight: 400;
    cursor: pointer;
  }
}

.radio-group,
.checkbox-group {
  display: flex;
  flex-direction: column;
  gap: var(--sm);
  width: 100%;
  margin-block-start: var(--sm);

  label {
    display: flex;
    align-items: center;
    gap: 0.6rem;
    width: 100%;
    font-weight: 400;
    cursor: pointer;
  }
}

.radio-group input[type="radio"],
.checkbox-group input[type="checkbox"] {
  width: auto;
  margin: 0;
  flex-shrink: 0;
}

.error-msg {
  color: var(--error);
  font-size: 0.9rem;
  margin-block-start: 0.3rem;
}

.form-actions {
  margin-block-start: var(--xl);
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  padding: 0.85rem 1.75rem;
  font: inherit;
  font-weight: 600;
  border: none;
  border-radius: var(--radius);
  cursor: pointer;
  transition: background-color var(--transition), transform var(--transition);
  text-decoration: none;
}

.btn--primary {
  background-color: var(--accent);
  color: oklch(0.15 0.02 280);

  &:hover,
  &:focus-visible {
    background-color: var(--accent-hover);
    transform: translateY(-2px);
    color: oklch(0.15 0.02 280);
  }
}

.btn--secondary {
  background-color: transparent;
  border: 1px solid var(--accent);
  color: var(--accent);

  &:hover {
    background-color: var(--accent-soft);
    color: var(--accent);
  }
}

footer {
  background-color: var(--surface);
  border-block-end: 1px solid var(--border);
  padding-block: var(--xl);
  margin-block-start: auto;
  text-align: center;
  font-size: 0.9rem;
  color: var(--text-muted);

  a {
    color: oklch(0.85 0.2 335);
    text-decoration: underline;
    text-underline-offset: 0.15em;

    &:hover,
    &:focus-visible {
      color: oklch(0.92 0.18 335);
    }
  }
}

.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  border: 0;
}

.text-center { text-align: center; }
.mt-lg { margin-block-start: var(--lg); }

@media (min-width: 40rem) {
  .nav-toggle {
    display: none;
  }

  .main-nav {
    display: flex;
    flex-direction: row;
    width: auto;
    padding-top: 0;
    gap: 0.25rem;
  }

  .flex-row {
    flex-direction: row;
    align-items: flex-start;
  }

  .flex-row > * {
    flex: 1;
  }

  .grid-cards {
    flex-direction: row;
    flex-wrap: wrap;
  }

  .grid-cards > * {
    flex: 1 1 calc(50% - var(--lg));
  }
}

@media (min-width: 60rem) {
  .grid-cards > * {
    flex: 1 1 calc(33.333% - var(--lg));
  }

  .home {
    padding-block: 6rem;
  }
}

:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 3px;
}