@import url('https://fonts.googleapis.com/css2?family=JetBrains+Mono:wght@400;600&family=Inter:wght@400;500;600;700&display=swap');

/* ── CSS VARIABLES ── */
:root {
  --bg: #0f1117;
  --surface: #1a1d27;
  --surface2: #232639;
  --border: #2e3250;
  --accent: #6c63ff;
  --accent2: #00d9a0;
  --text: #e2e4f0;
  --muted: #8890b0;
  --code-bg: #12141e;
  --white: #ffffff;
  --danger: #ff5f72;
  --warn: #ffb347;
  --sidebar-w: 260px;
}

/* ── RESET ── */
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: 'Inter', sans-serif;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

/* ════════════════════════════
   TOPBAR / HEADER
════════════════════════════ */
header {
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  padding: 0 24px;
  height: 56px;
  display: flex;
  align-items: center;
  gap: 20px;
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
}

.logo {
  font-family: 'JetBrains Mono', monospace;
  font-weight: 600;
  font-size: 18px;
  color: var(--white);
  display: flex;
  align-items: center;
  gap: 8px;
  text-decoration: none;
  flex-shrink: 0;
}

.logo-icon {
  width: 28px;
  height: 28px;
  background: linear-gradient(135deg, var(--accent), var(--accent2));
  border-radius: 6px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 14px;
}

/* ── SEARCH ── */
.search-bar {
  flex: 1;
  max-width: 400px;
  position: relative;
}

.search-bar input {
  width: 100%;
  background: var(--surface2);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 8px 14px 8px 38px;
  color: var(--text);
  font-family: 'Inter', sans-serif;
  font-size: 14px;
  outline: none;
  transition: border-color 0.2s;
}

.search-bar input:focus {
  border-color: var(--accent);
}

.search-bar input::placeholder {
  color: var(--muted);
}

.search-bar svg {
  position: absolute;
  left: 12px;
  top: 50%;
  transform: translateY(-50%);
  color: var(--muted);
}

/* ── NAV PILLS ── */
.nav-pills {
  display: flex;
  gap: 4px;
  margin-left: auto;
}

.nav-pill {
  padding: 6px 14px;
  border-radius: 6px;
  font-size: 13px;
  font-weight: 500;
  color: var(--muted);
  cursor: pointer;
  border: none;
  background: none;
  font-family: 'Inter', sans-serif;
  transition: color 0.2s, background 0.2s;
}

.nav-pill:hover {
  color: var(--text);
  background: var(--surface2);
}

.nav-pill.active {
  color: var(--white);
  background: var(--accent);
}

/* ════════════════════════════
   LAYOUT
════════════════════════════ */
.layout {
  display: flex;
  margin-top: 56px;
  flex: 1;
}

/* ════════════════════════════
   SIDEBAR
════════════════════════════ */
.sidebar {
  width: var(--sidebar-w);
  background: var(--surface);
  border-right: 1px solid var(--border);
  position: fixed;
  top: 56px;
  bottom: 0;
  left: 0;
  overflow-y: auto;
  padding: 16px 0;
}

.sidebar::-webkit-scrollbar {
  width: 4px;
}

.sidebar::-webkit-scrollbar-thumb {
  background: var(--border);
  border-radius: 4px;
}

.sidebar-section {
  margin-bottom: 8px;
}

.sidebar-heading {
  font-size: 10px;
  font-weight: 700;
  letter-spacing: 1.2px;
  text-transform: uppercase;
  color: var(--muted);
  padding: 10px 20px 4px;
}

.sidebar-item {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 9px 20px;
  font-size: 13.5px;
  color: var(--muted);
  cursor: pointer;
  border-left: 3px solid transparent;
  transition: color 0.15s, background 0.15s, border-color 0.15s;
}

.sidebar-item:hover {
  color: var(--text);
  background: var(--surface2);
}

.sidebar-item.active {
  color: var(--accent2);
  background: rgba(0, 217, 160, 0.06);
  border-left-color: var(--accent2);
  font-weight: 600;
}

.sidebar-item .tag {
  margin-left: auto;
  font-size: 10px;
  padding: 2px 7px;
  border-radius: 20px;
  background: rgba(108, 99, 255, 0.15);
  color: var(--accent);
  font-weight: 600;
}

.sidebar-item .tag.new {
  background: rgba(0, 217, 160, 0.12);
  color: var(--accent2);
}

/* ── PROGRESS ── */
.progress-bar-wrap {
  background: var(--surface2);
  border-radius: 4px;
  height: 4px;
  margin: 0 20px 16px;
  overflow: hidden;
}

.progress-bar-fill {
  height: 100%;
  width: 30%;
  background: linear-gradient(90deg, var(--accent), var(--accent2));
  border-radius: 4px;
}

.progress-label {
  font-size: 11px;
  color: var(--muted);
  padding: 0 20px;
  margin-bottom: 12px;
}

/* ════════════════════════════
   MAIN CONTENT AREA
════════════════════════════ */
.main {
  margin-left: var(--sidebar-w);
  flex: 1;
  display: flex;
  flex-direction: column;
}

.content {
  padding: 40px 48px;
  max-width: 880px;
}

/* ── BREADCRUMB ── */
.breadcrumb {
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 12px;
  color: var(--muted);
  margin-bottom: 28px;
}

.breadcrumb span {
  color: var(--accent);
}

/* ── PAGE TITLE / META ── */
.page-title {
  font-size: 32px;
  font-weight: 700;
  color: var(--white);
  margin-bottom: 8px;
  line-height: 1.2;
}

.page-meta {
  display: flex;
  align-items: center;
  gap: 16px;
  margin-bottom: 32px;
}

.badge {
  font-size: 11px;
  font-weight: 600;
  padding: 3px 10px;
  border-radius: 20px;
}

.badge-beginner     { background: rgba(0, 217, 160, 0.12); color: var(--accent2); }
.badge-intermediate { background: rgba(255, 179, 71, 0.12); color: var(--warn); }
.badge-advanced     { background: rgba(255, 95, 114, 0.12); color: var(--danger); }

.read-time {
  font-size: 12px;
  color: var(--muted);
}

/* ════════════════════════════
   PROSE (ARTICLE TEXT)
════════════════════════════ */
.prose {
  line-height: 1.75;
  font-size: 15px;
  color: #c0c8e0;
}

.prose h2 {
  font-size: 20px;
  font-weight: 700;
  color: var(--white);
  margin: 40px 0 14px;
}

.prose h3 {
  font-size: 16px;
  font-weight: 600;
  color: var(--text);
  margin: 28px 0 10px;
}

.prose p {
  margin-bottom: 18px;
}

.prose code {
  font-family: 'JetBrains Mono', monospace;
  font-size: 13px;
  background: var(--surface2);
  border: 1px solid var(--border);
  padding: 2px 7px;
  border-radius: 4px;
  color: var(--accent2);
}

.prose ul,
.prose ol {
  padding-left: 22px;
  margin-bottom: 18px;
}

.prose li {
  margin-bottom: 6px;
}

/* ── CALLOUTS ── */
.callout {
  border-left: 3px solid var(--accent);
  background: rgba(108, 99, 255, 0.07);
  padding: 14px 18px;
  border-radius: 0 8px 8px 0;
  margin: 24px 0;
  font-size: 14px;
  color: var(--text);
}

.callout-tip  { border-color: var(--accent2); background: rgba(0, 217, 160, 0.06); }
.callout-warn { border-color: var(--warn);    background: rgba(255, 179, 71, 0.06); }

.callout strong {
  display: block;
  font-size: 12px;
  letter-spacing: 0.5px;
  text-transform: uppercase;
  margin-bottom: 6px;
  color: var(--accent);
}

.callout-tip  strong { color: var(--accent2); }
.callout-warn strong { color: var(--warn); }

/* ════════════════════════════
   CODE BLOCKS
════════════════════════════ */
.code-block {
  background: var(--code-bg);
  border: 1px solid var(--border);
  border-radius: 10px;
  overflow: hidden;
  margin: 24px 0;
}

.code-toolbar {
  display: flex;
  align-items: center;
  padding: 10px 16px;
  background: var(--surface2);
  border-bottom: 1px solid var(--border);
  gap: 8px;
}

.code-dots {
  display: flex;
  gap: 6px;
  margin-right: 8px;
}

.code-dots span {
  width: 10px;
  height: 10px;
  border-radius: 50%;
}

.code-dots span:nth-child(1) { background: #ff5f57; }
.code-dots span:nth-child(2) { background: #febc2e; }
.code-dots span:nth-child(3) { background: #28c840; }

.code-lang {
  font-family: 'JetBrains Mono', monospace;
  font-size: 11px;
  font-weight: 600;
  color: var(--accent);
  letter-spacing: 0.5px;
  text-transform: uppercase;
}

.code-btn {
  margin-left: auto;
  display: flex;
  gap: 8px;
}

.btn-sm {
  font-size: 12px;
  font-weight: 500;
  padding: 5px 12px;
  border-radius: 6px;
  cursor: pointer;
  border: 1px solid var(--border);
  background: var(--surface);
  color: var(--muted);
  font-family: 'Inter', sans-serif;
  transition: color 0.2s, border-color 0.2s;
}

.btn-sm:hover {
  color: var(--text);
  border-color: var(--accent);
}

.btn-run {
  background: var(--accent2);
  color: #0a0e1a;
  border-color: var(--accent2);
  font-weight: 700;
}

.btn-run:hover {
  background: #00eaad;
  border-color: #00eaad;
  color: #0a0e1a;
}

.code-area {
  padding: 20px 24px;
  overflow-x: auto;
}

.code-area pre {
  font-family: 'JetBrains Mono', monospace;
  font-size: 13.5px;
  line-height: 1.75;
  color: var(--text);
  white-space: pre;
}

/* Syntax highlight classes */
.kw   { color: #c792ea; }
.fn   { color: #82aaff; }
.str  { color: #c3e88d; }
.num  { color: #f78c6c; }
.cm   { color: #546e7a; font-style: italic; }
.op   { color: #89ddff; }
.tag-c { color: #f07178; }
.attr { color: #ffcb6b; }

/* ════════════════════════════
   TRY IT EDITOR
════════════════════════════ */
.try-it-block {
  background: var(--code-bg);
  border: 1px solid var(--border);
  border-radius: 10px;
  overflow: hidden;
  margin: 28px 0;
}

.try-it-header {
  background: linear-gradient(90deg, rgba(108, 99, 255, 0.15), rgba(0, 217, 160, 0.1));
  border-bottom: 1px solid var(--border);
  padding: 10px 16px;
  display: flex;
  align-items: center;
  gap: 10px;
}

.try-it-header span {
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 0.5px;
  text-transform: uppercase;
  color: var(--accent2);
}

.try-it-body {
  display: flex;
  min-height: 200px;
}

.editor-pane,
.output-pane {
  flex: 1;
  min-width: 0;
}

.editor-pane {
  border-right: 1px solid var(--border);
}

.pane-label {
  font-size: 10px;
  font-weight: 600;
  letter-spacing: 1px;
  text-transform: uppercase;
  color: var(--muted);
  padding: 8px 14px;
  background: var(--surface2);
  border-bottom: 1px solid var(--border);
}

.code-editor {
  width: 100%;
  background: var(--code-bg);
  border: none;
  padding: 16px;
  color: var(--text);
  font-family: 'JetBrains Mono', monospace;
  font-size: 13px;
  line-height: 1.7;
  resize: none;
  outline: none;
  min-height: 180px;
}

.output-pane iframe {
  width: 100%;
  height: 100%;
  min-height: 180px;
  border: none;
  background: #fff;
}

.try-it-footer {
  display: flex;
  align-items: center;
  justify-content: flex-end;
  gap: 10px;
  padding: 10px 16px;
  background: var(--surface2);
  border-top: 1px solid var(--border);
}

/* ════════════════════════════
   TABLE
════════════════════════════ */
.data-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 14px;
  margin: 20px 0;
}

.data-table th {
  text-align: left;
  background: var(--surface2);
  color: var(--muted);
  font-weight: 600;
  font-size: 12px;
  letter-spacing: 0.5px;
  text-transform: uppercase;
  padding: 10px 14px;
  border: 1px solid var(--border);
}

.data-table td {
  padding: 10px 14px;
  border: 1px solid var(--border);
  color: var(--text);
  vertical-align: top;
}

.data-table tr:nth-child(even) td {
  background: rgba(255, 255, 255, 0.02);
}

.data-table td code {
  font-family: 'JetBrains Mono', monospace;
  font-size: 12px;
  color: var(--accent2);
}

/* ════════════════════════════
   LESSON NAVIGATION
════════════════════════════ */
.lesson-nav {
  display: flex;
  gap: 16px;
  margin-top: 48px;
  padding-top: 32px;
  border-top: 1px solid var(--border);
}

.nav-card {
  flex: 1;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 18px 20px;
  cursor: pointer;
  transition: border-color 0.2s, background 0.2s;
  text-decoration: none;
  color: inherit;
}

.nav-card:hover {
  border-color: var(--accent);
  background: var(--surface2);
}

.nav-card.next {
  text-align: right;
}

.nav-card-label {
  font-size: 11px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  color: var(--muted);
  margin-bottom: 6px;
}

.nav-card-title {
  font-size: 15px;
  font-weight: 600;
  color: var(--white);
}

/* ════════════════════════════
   RESPONSIVE
════════════════════════════ */
@media (max-width: 768px) {
  .sidebar       { display: none; }
  .main          { margin-left: 0; }
  .content       { padding: 24px 18px; }
  .try-it-body   { flex-direction: column; }
  .editor-pane   { border-right: none; border-bottom: 1px solid var(--border); }
  .nav-pills     { display: none; }
  .page-title    { font-size: 24px; }
  .lesson-nav    { flex-direction: column; }
}