:root {
  --bg: #12141a;
  --panel: #1c2028;
  --text: #e8eaed;
  --muted: #9aa3ad;
  --line: #2a3038;
  --accent: #3d9a78;
  --danger: #d4786a;
  --ok: #7cbc8c;
}

* {
  box-sizing: border-box;
}

[hidden] {
  display: none !important;
}

html,
body {
  margin: 0;
  height: 100%;
  background: var(--bg);
  color: var(--text);
  font: 15px/1.45 ui-sans-serif, system-ui, -apple-system, "Segoe UI", sans-serif;
}

.app:not([hidden]) {
  display: grid;
  grid-template-columns: 220px 1fr;
  grid-template-rows: auto 1fr;
  height: 100vh;
}

.stage {
  display: grid;
  grid-template-columns: minmax(260px, 36%) 1fr;
  min-height: 0;
  position: relative;
}

.app.practice-off .stage {
  grid-template-columns: 1fr;
}

.top {
  grid-column: 1 / -1;
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 16px;
  padding: 10px 16px;
  border-bottom: 1px solid var(--line);
  background: var(--panel);
}

.brand {
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: 13px;
  color: var(--accent);
  letter-spacing: 0.04em;
}

.top h1 {
  flex: 1;
  margin: 0;
  font-size: 16px;
  font-weight: 600;
}

button {
  background: transparent;
  border: 1px solid var(--line);
  color: var(--text);
  padding: 7px 12px;
  border-radius: 6px;
  font: inherit;
  cursor: pointer;
}

#check-btn:hover:not(:disabled) {
  border-color: var(--accent);
  color: var(--accent);
}

#hint-btn:hover:not(:disabled) {
  border-color: var(--accent);
  color: var(--accent);
}

#complete-btn:hover:not(:disabled) {
  border-color: var(--accent);
  color: var(--accent);
}

#reset-btn:hover:not(:disabled) {
  border-color: var(--danger);
  color: var(--danger);
}

button:disabled {
  opacity: 0.55;
  cursor: default;
}

.nav {
  overflow: auto;
  padding: 16px 12px 24px;
  border-right: 1px solid var(--line);
  background: var(--bg);
  position: relative;
  z-index: 4;
}

.nav .module {
  margin: 0 8px 8px;
  font-size: 12px;
  font-weight: 650;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--muted);
}

.nav .module:not(:first-child) {
  margin-top: 44px;
}

.nav a {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
  color: var(--text);
  text-decoration: none;
  padding: 7px 8px;
  border-radius: 6px;
}

.nav a:hover {
  background: var(--panel);
}

.nav a.current {
  background: var(--panel);
  color: var(--accent);
}

.nav a.locked {
  color: var(--muted);
}

.nav a.locked:hover {
  background: var(--panel);
}

.nav .icon {
  display: flex;
  flex-shrink: 0;
  color: var(--muted);
}

.nav a.done .icon {
  color: var(--ok);
}

.pages {
  display: flex;
  gap: 8px;
  margin: 0 0 16px;
  position: relative;
  z-index: 4;
}

.pages a {
  color: var(--muted);
  text-decoration: none;
  padding: 6px 10px;
  border-radius: 6px;
  border: 1px solid var(--line);
  font-size: 13px;
}

.pages a:hover {
  color: var(--text);
  background: var(--bg);
}

.pages a.current {
  color: var(--accent);
  border-color: var(--accent);
}

.lock-veil {
  position: absolute;
  inset: 0;
  z-index: 3;
  display: grid;
  place-items: center;
  align-content: center;
  gap: 10px;
  color: var(--text);
  background: rgba(18, 20, 26, 0.28);
}

.lock-veil[hidden] {
  display: none !important;
}

.lock-veil p {
  margin: 0;
  font-size: 15px;
  font-weight: 600;
}

.app.locked .lesson {
  overflow: hidden;
}

.app.locked .lesson > *:not(.pages) {
  filter: blur(7px);
  pointer-events: none;
  user-select: none;
}

.app.locked .term-wrap {
  filter: blur(7px);
  pointer-events: none;
  user-select: none;
}

.lesson {
  overflow: auto;
  padding: 20px 22px 32px;
  border-right: 1px solid var(--line);
  background: var(--panel);
}

.lesson h2 {
  margin: 0 0 10px;
  font-size: 12px;
  font-weight: 650;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--muted);
}

.ns-line {
  margin: 0 0 16px;
  font: 13px/1.4 ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  color: var(--accent);
}

.lesson section + section {
  margin-top: 28px;
  padding-top: 22px;
  border-top: 1px solid var(--line);
}

#hint-section {
  margin-top: 22px;
  padding-top: 18px;
  border-top: 1px dashed var(--line);
}

.md h1,
.md h2,
.md h3 {
  line-height: 1.25;
}

.md h1 {
  font-size: 1.35rem;
  margin: 0 0 12px;
}

.md p,
.md li {
  color: var(--text);
}

.md code {
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: 0.92em;
  background: var(--bg);
  padding: 0.1em 0.35em;
  border-radius: 4px;
}

.md pre {
  background: var(--bg);
  padding: 12px 14px;
  border-radius: 6px;
  overflow: auto;
}

.md pre code {
  padding: 0;
  background: none;
}

.status {
  margin: 0 0 16px;
  padding: 8px 10px;
  border-radius: 6px;
  font-size: 13px;
  white-space: pre-wrap;
}

.status.ok {
  color: var(--ok);
  border: 1px solid #2f4a38;
}

.status.err {
  color: var(--danger);
  border: 1px solid #5a322e;
}

.term-wrap {
  min-height: 0;
  background: #0d1117;
  padding: 8px;
}

#terminal {
  height: 100%;
  width: 100%;
}

@media (max-width: 960px) {
  .app {
    grid-template-columns: 1fr;
    grid-template-rows: auto auto 1fr;
  }

  .stage {
    grid-template-columns: 1fr;
    grid-template-rows: auto minmax(40vh, 1fr);
  }

  .app.practice-off .stage {
    grid-template-rows: 1fr;
  }

  .nav {
    border-right: none;
    border-bottom: 1px solid var(--line);
    max-height: 22vh;
  }

  .lesson {
    border-right: none;
    border-bottom: 1px solid var(--line);
    max-height: 36vh;
  }

  .top {
    flex-wrap: wrap;
  }
}

.who {
  color: var(--muted);
  font-size: 13px;
}

.gate:not([hidden]) {
  min-height: 100%;
  display: grid;
  place-items: center;
  padding: 24px;
}

.gate-card {
  width: min(360px, 100%);
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 10px;
  padding: 22px 22px 18px;
  display: grid;
  gap: 12px;
}

.gate-card h1 {
  margin: 4px 0 4px;
  font-size: 1.25rem;
}

.gate-card label {
  display: grid;
  gap: 6px;
  font-size: 13px;
  color: var(--muted);
}

.gate-card input {
  background: var(--bg);
  border: 1px solid var(--line);
  color: var(--text);
  padding: 8px 10px;
  border-radius: 6px;
  font: inherit;
}

.gate-card button[type="submit"] {
  border-color: var(--accent);
  color: var(--accent);
}

.admin:not([hidden]) {
  min-height: 100%;
  display: grid;
  grid-template-rows: auto 1fr;
}

.admin-body {
  padding: 22px;
  overflow: auto;
}

.admin-create {
  display: flex;
  flex-wrap: wrap;
  gap: 12px 16px;
  align-items: end;
  margin: 0 0 28px;
  padding: 16px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--panel);
}

.admin-create h2 {
  flex: 1 0 100%;
  margin: 0;
  font-size: 12px;
  font-weight: 650;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--muted);
}

.admin-create label {
  display: grid;
  gap: 6px;
  font-size: 13px;
  color: var(--muted);
}

.admin-create input,
.admin-create select {
  background: var(--bg);
  border: 1px solid var(--line);
  color: var(--text);
  padding: 8px 10px;
  border-radius: 6px;
  font: inherit;
}

.admin-create button {
  border-color: var(--accent);
  color: var(--accent);
}

.users {
  width: 100%;
  border-collapse: collapse;
}

.users th,
.users td {
  text-align: left;
  padding: 8px 10px;
  border-bottom: 1px solid var(--line);
}

.users th {
  font-size: 12px;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--muted);
  font-weight: 650;
}

.users td:last-child {
  white-space: nowrap;
  text-align: right;
}

.users td:last-child button + button {
  margin-left: 8px;
}

.users .danger:hover:not(:disabled) {
  border-color: var(--danger);
  color: var(--danger);
}

.users select {
  background: var(--bg);
  border: 1px solid var(--line);
  color: var(--text);
  padding: 6px 8px;
  border-radius: 6px;
  font: inherit;
}

.admin-hint {
  margin: 0 0 16px;
  font-size: 13px;
  color: var(--muted);
  max-width: 52rem;
}

.users .unlock-on {
  border-color: var(--accent);
  color: var(--accent);
}

.users td:nth-child(4) {
  white-space: nowrap;
}

.users td:nth-child(4) button {
  min-width: 9.5rem;
}

@media (max-width: 860px) {
  .users th:nth-child(3),
  .users td:nth-child(3) {
    display: none;
  }
}