:root {
  --base-font-size: 16px;
  --bg: #0b1020;
  --bg-soft: #121a33;
  --surface: rgba(12, 18, 36, 0.8);
  --surface-solid: #111933;
  --surface-light: rgba(173, 201, 255, 0.08);
  --ink: #eaf0ff;
  --ink-dim: #b4c1dd;
  --line: rgba(181, 201, 255, 0.2);
  --line-strong: rgba(181, 201, 255, 0.4);
  --accent: #8aa7ff;
  --accent-2: #65f0d1;
  --ok: #45d483;
  --warn: #f7c66f;
  --err: #ff7f93;
  --shadow-soft: 0 14px 36px rgba(4, 9, 20, 0.35);
  --shadow-strong: 0 22px 60px rgba(4, 9, 20, 0.5);
}

* {
  box-sizing: border-box;
}

html {
  font-size: var(--base-font-size);
}

body {
  margin: 0;
  min-height: 100vh;
  color: var(--ink);
  font-family: "Space Grotesk", system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  line-height: 1.6;
  background:
    radial-gradient(1200px 600px at 10% -10%, rgba(138, 167, 255, 0.28), transparent 62%),
    radial-gradient(1200px 700px at 100% 0%, rgba(101, 240, 209, 0.2), transparent 58%),
    linear-gradient(160deg, #090e1c 0%, #0c1429 44%, #0b1020 100%);
  background-attachment: fixed;
  -webkit-font-smoothing: antialiased;
}

.layout {
  width: min(1200px, calc(100% - 48px));
  margin: 28px auto 48px;
  position: relative;
}

.layout::before {
  content: "";
  position: absolute;
  inset: -1px;
  border-radius: 24px;
  background: linear-gradient(130deg, rgba(138, 167, 255, 0.32), rgba(101, 240, 209, 0.2));
  z-index: 0;
  filter: blur(16px);
  opacity: 0.45;
}

.menu-toggle {
  position: fixed;
  top: 18px;
  left: 18px;
  width: 48px;
  height: 48px;
  border-radius: 14px;
  border: 1px solid var(--line-strong);
  background: rgba(10, 15, 30, 0.85);
  color: var(--ink);
  font-size: 1.2rem;
  line-height: 1;
  cursor: pointer;
  z-index: 50;
  box-shadow: var(--shadow-soft);
  transition: transform 120ms ease, background 180ms ease, border-color 180ms ease;
}

.menu-toggle:hover {
  transform: translateY(-1px);
  background: rgba(15, 22, 44, 0.95);
  border-color: rgba(138, 167, 255, 0.6);
}

.side-drawer {
  position: fixed;
  top: 18px;
  left: 18px;
  width: min(360px, calc(100vw - 36px));
  max-height: calc(100vh - 36px);
  padding: 18px 16px;
  border-radius: 18px;
  border: 1px solid var(--line);
  background: linear-gradient(150deg, rgba(17, 25, 50, 0.94), rgba(11, 18, 37, 0.94));
  backdrop-filter: blur(10px);
  box-shadow: var(--shadow-strong);
  overflow-y: auto;
  transform: translateX(-115%);
  opacity: 0;
  pointer-events: none;
  transition: transform 220ms ease, opacity 220ms ease;
  z-index: 45;
}

body.drawer-open .side-drawer {
  transform: translateX(0);
  opacity: 1;
  pointer-events: auto;
}

.drawer-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
  margin-bottom: 12px;
}

.drawer-head h2 {
  margin: 0;
  font-size: 1.08rem;
  letter-spacing: 0.02em;
}

.menu-close {
  width: 36px;
  height: 36px;
  border-radius: 10px;
  border: 1px solid var(--line);
  background: rgba(17, 25, 50, 0.7);
  color: var(--ink);
  font-size: 1.05rem;
  cursor: pointer;
}

.drawer-nav {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 8px;
  margin-bottom: 14px;
}

.drawer-font-control {
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
  padding: 12px 0;
  margin-bottom: 14px;
}

.font-control {
  display: grid;
  grid-template-columns: auto 1fr auto auto;
  align-items: center;
  gap: 8px;
}

.font-control label {
  font-size: 0.88rem;
  color: var(--ink-dim);
}

.font-control input[type="range"] {
  width: 100%;
}

.tiny-btn {
  padding: 5px 10px;
  font-size: 0.78rem;
}

.monitor-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 8px;
  border-top: 1px dashed rgba(181, 201, 255, 0.18);
  padding: 9px 0;
  font-size: 0.9rem;
}

.status-pill {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  border: 1px solid var(--line);
  border-radius: 999px;
  padding: 2px 10px;
  font-size: 0.74rem;
  letter-spacing: 0.03em;
}

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

.status-warn {
  color: var(--warn);
}

.status-err {
  color: var(--err);
}

.error-feed {
  margin: 0;
  padding-left: 18px;
  max-height: 180px;
  overflow: auto;
  font-size: 0.85rem;
  color: var(--ink-dim);
}

.shell {
  position: relative;
  z-index: 1;
  border: 1px solid var(--line);
  border-radius: 22px;
  background: linear-gradient(180deg, rgba(14, 21, 40, 0.9), rgba(10, 16, 31, 0.92));
  backdrop-filter: blur(10px);
  box-shadow: var(--shadow-strong);
  overflow: hidden;
}

.shell::before {
  content: "";
  position: absolute;
  inset: 0;
  background: linear-gradient(145deg, rgba(138, 167, 255, 0.08), transparent 28%, transparent 72%, rgba(101, 240, 209, 0.08));
  pointer-events: none;
}

.hero {
  position: relative;
  padding: 28px 26px 20px;
  border-bottom: 1px solid var(--line);
}

.brand {
  display: flex;
  align-items: center;
  gap: 14px;
}

.brand-logo {
  width: 58px;
  height: 58px;
  border-radius: 14px;
  border: 1px solid var(--line-strong);
  background: rgba(15, 22, 44, 0.5);
  padding: 8px;
}

.eyebrow {
  margin: 0;
  font-size: 0.68rem;
  text-transform: uppercase;
  letter-spacing: 0.16em;
  color: var(--ink-dim);
}

h1 {
  margin: 2px 0 0;
  font-size: clamp(1.8rem, 3.3vw, 3rem);
  line-height: 1.1;
  font-weight: 700;
}

.hero p {
  margin: 10px 0 0;
  color: var(--ink-dim);
}

.hero-menu-hint {
  margin-top: 14px;
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 6px 10px;
  border-radius: 999px;
  border: 1px solid var(--line);
  background: var(--surface-light);
  color: var(--ink);
  font-size: 0.82rem;
}

.panel {
  padding: 20px 26px;
  border-bottom: 1px solid var(--line);
}

.panel:last-of-type {
  border-bottom: none;
}

.reveal {
  animation: fadeUp 300ms ease both;
}

@keyframes fadeUp {
  from {
    opacity: 0;
    transform: translateY(10px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

h2 {
  margin: 0;
  font-size: 1.12rem;
  font-weight: 600;
}

h3 {
  margin: 0;
  font-size: 0.95rem;
  font-weight: 600;
}

h4 {
  margin: 0;
  font-size: 0.94rem;
  font-weight: 600;
}

.hint {
  margin-top: 6px;
  color: var(--ink-dim);
  font-size: 0.88rem;
}

.mode-badge {
  display: inline-flex;
  margin-top: 8px;
  padding: 4px 10px;
  border-radius: 999px;
  border: 1px solid rgba(138, 167, 255, 0.4);
  background: rgba(138, 167, 255, 0.14);
  color: #d8e1ff;
  font-size: 0.8rem;
}

.stack {
  display: grid;
  gap: 10px;
}

.mode-row {
  display: flex;
  gap: 8px;
  align-items: center;
  flex-wrap: wrap;
}

label {
  font-size: 0.88rem;
  font-weight: 500;
  color: #d8e1ff;
}

textarea,
input[type="file"],
select {
  width: 100%;
  font: inherit;
  color: var(--ink);
}

textarea,
select {
  border-radius: 12px;
  border: 1px solid var(--line);
  background: rgba(14, 21, 40, 0.8);
  padding: 10px 12px;
}

textarea {
  min-height: 220px;
  resize: vertical;
}

textarea:focus,
select:focus,
button:focus,
.button-link:focus,
input[type="file"]:focus {
  outline: 2px solid rgba(138, 167, 255, 0.55);
  outline-offset: 2px;
}

input[type="file"] {
  font-size: 0.9rem;
}

input[type="file"]::file-selector-button {
  margin-right: 10px;
  border-radius: 10px;
  border: 1px solid var(--line);
  background: rgba(14, 21, 40, 0.8);
  color: var(--ink);
  padding: 6px 11px;
  font: inherit;
  cursor: pointer;
}

button,
.button-link {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 7px;
  border-radius: 999px;
  border: 1px solid rgba(138, 167, 255, 0.45);
  background: linear-gradient(120deg, #8aa7ff, #65f0d1);
  color: #081226;
  padding: 8px 14px;
  font: inherit;
  font-weight: 700;
  font-size: 0.88rem;
  text-decoration: none;
  cursor: pointer;
  transition: transform 120ms ease, box-shadow 160ms ease, filter 160ms ease;
}

button:hover,
.button-link:hover {
  transform: translateY(-1px);
  box-shadow: 0 8px 20px rgba(101, 240, 209, 0.2);
  filter: saturate(1.1);
}

.button-link.secondary-link,
button.secondary {
  background: rgba(17, 25, 50, 0.75);
  color: var(--ink);
  border-color: var(--line);
  font-weight: 500;
}

.actions {
  margin-top: 12px;
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.summary-grid {
  margin-top: 10px;
  display: grid;
  grid-template-columns: 1fr;
  gap: 12px;
}

article,
.history-item,
.question,
.lecture-toggle {
  border: 1px solid var(--line);
  border-radius: 14px;
  background: rgba(13, 20, 39, 0.72);
  box-shadow: var(--shadow-soft);
}

article,
.question,
.history-item {
  padding: 12px;
}

.history-list {
  margin-top: 12px;
  display: grid;
  gap: 12px;
}

.history-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
}

.history-preview {
  margin: 8px 0 0;
  color: var(--ink-dim);
  font-size: 0.92rem;
}

.lecture-toggle {
  margin-top: 12px;
  overflow: hidden;
}

.lecture-toggle summary {
  list-style: none;
  cursor: pointer;
  padding: 11px 12px;
  font-weight: 600;
  border-bottom: 1px solid var(--line);
  background: rgba(138, 167, 255, 0.08);
}

.lecture-toggle summary::-webkit-details-marker {
  display: none;
}

.lecture-toggle[open] summary {
  color: #d9e3ff;
}

.note-body {
  display: grid;
  gap: 8px;
}

.note-line,
.note-section,
.note-formula,
.note-important {
  margin: 0;
}

.note-line {
  color: #d4def8;
  font-size: 0.95rem;
}

.note-section {
  padding: 8px 10px;
  border-radius: 10px;
  border: 1px solid var(--line);
  background: rgba(138, 167, 255, 0.08);
  color: #e6edff;
}

.note-formula {
  font-family: "Source Serif 4", serif;
  font-size: 1.03rem;
  color: #c6ffd8;
}

.note-important {
  padding: 8px 10px;
  border-left: 3px solid var(--accent-2);
  border-radius: 8px;
  background: rgba(101, 240, 209, 0.08);
}

.note-spacer {
  height: 2px;
}

.question h4 {
  display: flex;
  align-items: center;
  gap: 10px;
}

.question-badge {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 38px;
  border-radius: 999px;
  border: 1px solid var(--line);
  background: rgba(138, 167, 255, 0.12);
  color: #d8e1ff;
  padding: 3px 9px;
  font-size: 0.74rem;
}

.options {
  display: grid;
  gap: 7px;
  margin-top: 8px;
}

.option {
  display: flex;
  align-items: flex-start;
  gap: 8px;
  border-radius: 10px;
  border: 1px solid transparent;
  background: rgba(17, 25, 50, 0.55);
  padding: 7px 9px;
  transition: border-color 140ms ease, background 140ms ease;
}

.option:hover {
  border-color: rgba(138, 167, 255, 0.35);
  background: rgba(23, 33, 66, 0.7);
}

.error {
  margin-top: 10px;
  color: var(--err);
  font-weight: 500;
}

.result-score,
.mastered {
  font-weight: 700;
}

.mastered {
  color: #c8ffd9;
}

pre {
  margin: 8px 0 0;
  white-space: pre-wrap;
  word-break: break-word;
  font-family: "Source Serif 4", serif;
  font-size: 0.95rem;
  color: #e9efff;
}

.hidden {
  display: none;
}

::-webkit-scrollbar {
  width: 10px;
  height: 10px;
}

::-webkit-scrollbar-thumb {
  background: rgba(138, 167, 255, 0.35);
  border-radius: 999px;
}

::-webkit-scrollbar-track {
  background: rgba(11, 16, 32, 0.45);
}

@media (max-width: 900px) {
  .layout {
    width: calc(100% - 20px);
    margin: 72px auto 20px;
  }

  .menu-toggle {
    top: 10px;
    left: 10px;
  }

  .shell {
    border-radius: 18px;
  }

  .hero,
  .panel {
    padding-left: 14px;
    padding-right: 14px;
  }

  .drawer-nav {
    grid-template-columns: 1fr;
  }

  .font-control {
    grid-template-columns: 1fr;
    align-items: stretch;
  }
}