:root {
  color-scheme: light;
  --bg: #f7f7f5;
  --surface: #ffffff;
  --surface-soft: #eeeeeb;
  --text: #25272b;
  --muted: #62676f;
  --line: #dbdcd8;
  --sidebar: #454746;
  --sidebar-strong: #393b3a;
  --sidebar-text: #f4f5f2;
  --sidebar-muted: #cfd2cc;
  --accent: #16a37a;
  --accent-soft: #dcf7ee;
  --danger: #b94949;
  --shadow: 0 16px 50px rgba(0, 0, 0, 0.12);
  --reader-width: 76rem;
  --base-font-scale: 1;
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

:root[data-theme="dark"] {
  color-scheme: dark;
  --bg: #1f2120;
  --surface: #292b2a;
  --surface-soft: #343735;
  --text: #f2f3ef;
  --muted: #b5bbb5;
  --line: #464a47;
  --sidebar: #141615;
  --sidebar-strong: #0f1110;
  --sidebar-text: #f5f6f3;
  --sidebar-muted: #abb2ac;
  --accent: #49d6ad;
  --accent-soft: #14362d;
  --shadow: 0 16px 50px rgba(0, 0, 0, 0.35);
}

:root[data-theme="warm"] {
  --bg: #f4f1ea;
  --surface: #fffdf7;
  --surface-soft: #e9e2d4;
  --text: #282623;
  --muted: #665f55;
  --line: #d9d0c0;
  --sidebar: #42413d;
  --sidebar-strong: #363530;
  --accent: #0f8d80;
  --accent-soft: #d9f1ed;
}

:root[data-font-family="serif"] { font-family: Georgia, "Times New Roman", serif; }
:root[data-font-family="mono"] { font-family: "SFMono-Regular", Consolas, monospace; }
:root[data-font-family="rounded"] { font-family: ui-rounded, "Nunito Sans", "Segoe UI", sans-serif; }

* { box-sizing: border-box; }

html {
  min-height: 100%;
  background: var(--bg);
  color: var(--text);
  font-size: calc(16px * var(--base-font-scale));
}

body {
  min-height: 100vh;
  margin: 0;
}

button,
select {
  font: inherit;
}

button {
  cursor: pointer;
}

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

.topbar {
  position: sticky;
  top: 0;
  z-index: 50;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  min-height: 4.5rem;
  padding: 0.75rem clamp(1rem, 3vw, 3rem);
  background: color-mix(in srgb, var(--surface) 92%, transparent);
  border-bottom: 1px solid var(--line);
  backdrop-filter: blur(16px);
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 0.7rem;
  min-width: 0;
}

.brand-mark {
  display: grid;
  place-items: center;
  width: 2.2rem;
  height: 2.2rem;
  border: 3px solid var(--text);
  border-radius: 0.55rem 0.55rem 0.55rem 0.1rem;
  color: var(--accent);
  font-weight: 900;
  line-height: 1;
}

.brand strong {
  display: block;
  font-size: clamp(1.05rem, 2vw, 1.35rem);
  line-height: 1.1;
}

.brand small {
  display: block;
  max-width: 60vw;
  overflow: hidden;
  color: var(--muted);
  font-size: 0.78rem;
  line-height: 1.2;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.top-actions {
  display: flex;
  align-items: center;
  gap: 0.45rem;
}

.icon-button {
  display: inline-grid;
  place-items: center;
  min-width: 2.45rem;
  height: 2.45rem;
  padding: 0 0.65rem;
  border: 1px solid var(--line);
  border-radius: 0.5rem;
  background: var(--surface);
  color: var(--text);
  font-weight: 800;
}

.icon-button:hover,
.icon-button:focus-visible {
  border-color: var(--accent);
  outline: none;
}

.language-button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.35rem;
  min-width: 4rem;
}

.language-icon {
  display: inline-grid;
  place-items: center;
  width: 1.05rem;
  height: 1.05rem;
  border: 2px solid currentColor;
  border-radius: 50%;
  font-size: 0.62rem;
  font-weight: 900;
  line-height: 1;
}

.language-code {
  min-width: 1.3rem;
  text-align: center;
  line-height: 1;
}

.font-button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.1rem;
  min-width: 2.95rem;
  line-height: 1;
}

.font-icon-large {
  display: block;
  font-size: 1rem;
  line-height: 1;
}

.font-icon-small {
  display: block;
  padding-top: 0.12rem;
  font-size: 0.62rem;
  line-height: 1;
}

.font-menu {
  position: relative;
}

.popover {
  position: absolute;
  top: calc(100% + 0.6rem);
  right: 0;
  z-index: 90;
  width: min(18rem, calc(100vw - 2rem));
  padding: 1rem;
  border: 1px solid var(--line);
  border-radius: 0.5rem;
  background: var(--surface);
  box-shadow: var(--shadow);
}

.stepper {
  display: grid;
  grid-template-columns: 2.5rem 1fr 2.5rem;
  align-items: center;
  gap: 0.5rem;
  margin-bottom: 0.85rem;
}

.stepper button {
  height: 2.35rem;
  border: 1px solid var(--line);
  border-radius: 0.45rem;
  background: var(--surface-soft);
  color: var(--text);
  font-weight: 900;
}

.stepper span {
  text-align: center;
  color: var(--muted);
  font-weight: 800;
}

.field {
  display: grid;
  gap: 0.4rem;
  color: var(--muted);
  font-size: 0.9rem;
  font-weight: 700;
}

.field select {
  width: 100%;
  min-height: 2.45rem;
  border: 1px solid var(--line);
  border-radius: 0.45rem;
  background: var(--surface);
  color: var(--text);
}

.home {
  max-width: 72rem;
  margin: 0 auto;
  padding: clamp(2rem, 5vw, 5rem) clamp(1rem, 4vw, 2rem);
}

.home-hero {
  max-width: 48rem;
  margin-bottom: 2rem;
}

.home-hero h1 {
  margin: 0 0 1rem;
  font-size: clamp(2rem, 6vw, 4rem);
  line-height: 1.04;
}

.home-hero p {
  margin: 0;
  color: var(--muted);
  font-size: 1.15rem;
  line-height: 1.7;
}

.semester-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1rem;
}

.semester-card {
  display: flex;
  min-height: 10.5rem;
  flex-direction: column;
  justify-content: space-between;
  padding: 1.35rem;
  border: 1px solid var(--line);
  border-radius: 0.5rem;
  background: var(--surface);
  box-shadow: 0 1px 0 rgba(0, 0, 0, 0.03);
  transition: transform 160ms ease, border-color 160ms ease, box-shadow 160ms ease;
}

.semester-card:hover,
.semester-card:focus-visible {
  border-color: var(--accent);
  box-shadow: var(--shadow);
  outline: none;
  transform: translateY(-2px);
}

.semester-card span {
  color: var(--accent);
  font-weight: 900;
  text-transform: uppercase;
}

.semester-card h2 {
  margin: 0.55rem 0;
  font-size: clamp(1.3rem, 3vw, 2rem);
}

.semester-card p {
  margin: 0;
  color: var(--muted);
  line-height: 1.55;
}

.empty-state {
  max-width: 48rem;
  margin: 5rem auto;
  padding: 0 1rem;
  color: var(--muted);
  text-align: center;
}

@media (max-width: 720px) {
  .topbar {
    min-height: 4rem;
  }

  .brand small {
    display: none;
  }

  .semester-grid {
    grid-template-columns: 1fr;
  }
}