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

:root {
  --bg: #0a0d13;
  --bg-panel: #11151d;
  --bg-panel-hover: #171c26;
  --bg-input: #0d1119;
  --border: #1e2733;
  --border-soft: #171f2a;
  --text: #c9d3de;
  --text-dim: #5c6773;
  --cyan: #5eeacf;
  --cyan-dim: #1c4a41;
  --amber: #f0b429;
  --danger: #ef6a5a;
  --mono: 'JetBrains Mono', monospace;
  --sans: 'Inter', -apple-system, sans-serif;
  --display: 'Space Grotesk', sans-serif;
}

[data-theme="light"] {
  --bg: #f0f4f8;
  --bg-panel: #ffffff;
  --bg-panel-hover: #e8edf3;
  --bg-input: #f8fafc;
  --border: #d1dbe6;
  --border-soft: #e2e8f0;
  --text: #1a2332;
  --text-dim: #64748b;
  --cyan: #0891b2;
  --cyan-dim: #cffafe;
  --amber: #d97706;
  --danger: #dc2626;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; background: var(--bg); }
body {
  font-family: var(--sans);
  margin: 0;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  position: relative;
  overflow-x: hidden;
}

/* ===== Nền: lưới + glow (đồng bộ với login) ===== */
body::before {
  content: "";
  position: fixed; inset: 0;
  background-image:
    linear-gradient(rgba(94,234,207,0.04) 1px, transparent 1px),
    linear-gradient(90deg, rgba(94,234,207,0.04) 1px, transparent 1px);
  background-size: 42px 42px;
  -webkit-mask-image: radial-gradient(ellipse 80% 55% at 50% 0%, #000 40%, transparent 90%);
          mask-image: radial-gradient(ellipse 80% 55% at 50% 0%, #000 40%, transparent 90%);
  pointer-events: none;
  z-index: 0;
}
body::after {
  content: "";
  position: fixed;
  width: 1100px; height: 900px;
  top: -280px; left: 50%;
  transform: translateX(-50%);
  background: radial-gradient(circle, rgba(94,234,207,0.09) 0%, rgba(94,234,207,0) 60%);
  pointer-events: none;
  z-index: 0;
}

/* ===== Lớp fx động chèn bằng app.js (radar + scanline) ===== */
.fx-layer { position: fixed; inset: 0; pointer-events: none; z-index: 0; overflow: hidden; }
.fx-radar {
  position: absolute; top: -160px; left: 50%;
  transform: translateX(-50%);
  width: 640px; height: 640px;
}
.fx-radar span {
  position: absolute; inset: 0;
  border: 1px solid rgba(94,234,207,0.10);
  border-radius: 50%;
  animation: ping 4.6s ease-out infinite;
}
.fx-radar span:nth-child(2) { animation-delay: 1.5s; }
.fx-radar span:nth-child(3) { animation-delay: 3s; }
@keyframes ping {
  0% { transform: scale(0.25); opacity: 0; }
  15% { opacity: 0.8; }
  100% { transform: scale(1); opacity: 0; }
}
.fx-scanline {
  position: absolute; inset: 0;
  background: linear-gradient(rgba(94,234,207,0.02) 50%, transparent 50%);
  background-size: 100% 4px;
  animation: scan 10s linear infinite;
  opacity: 0.45;
}
@keyframes scan { from { background-position-y: 0; } to { background-position-y: 1000px; } }

/* ===== Nav ===== */
nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 16px 32px;
  background: var(--bg-panel);
  backdrop-filter: blur(14px);
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  z-index: 20;
}
nav h1 {
  font-family: var(--mono);
  font-size: 17px;
  margin: 0;
  font-weight: 700;
  letter-spacing: -0.02em;
  color: var(--text);
}
nav h1::before { content: "$ "; color: var(--cyan); }
#nav-auth { display: flex; align-items: center; gap: 8px; }
nav a, nav button {
  color: var(--text);
  text-decoration: none;
  background: var(--bg-panel);
  border: 1px solid var(--border);
  padding: 8px 14px;
  border-radius: 7px;
  cursor: pointer;
  font-size: 13px;
  font-family: var(--sans);
  font-weight: 500;
  transition: all 0.15s ease;
  display: inline-flex;
  align-items: center;
  gap: 7px;
}
nav a:hover, nav button:hover {
  background: var(--bg-panel-hover);
  border-color: var(--cyan-dim);
  color: var(--cyan);
}
.nav-admin { color: var(--amber) !important; border-color: #4a3c14 !important; }
.nav-admin:hover { background: rgba(240,179,41,0.08) !important; }
#nav-username {
  font-family: var(--mono);
  color: var(--cyan);
  font-size: 13px;
  background: rgba(94,234,207,0.06);
  border: 1px solid var(--cyan-dim);
  padding: 7px 12px;
  border-radius: 7px;
  align-items: center;
  gap: 7px;
}

/* ===== Layout ===== */
main {
  max-width: 900px;
  margin: 0 auto;
  padding: 44px 24px 80px;
  position: relative;
  z-index: 1;
}
main h2 {
  font-family: var(--mono);
  font-size: 13px;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--text-dim);
  margin: 0 0 18px;
  display: flex;
  align-items: center;
  gap: 12px;
}
main h2::after { content: ""; flex: 1; height: 1px; background: var(--border); }

/* ===== Hero ===== */
.hero { margin-bottom: 34px; }
.hero .tag {
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--cyan);
  display: inline-flex;
  align-items: center;
  gap: 8px;
  margin-bottom: 14px;
}
.hero .tag .dot {
  width: 7px; height: 7px; border-radius: 50%;
  background: var(--cyan); box-shadow: 0 0 8px var(--cyan);
  animation: pulse 2s ease-in-out infinite;
}
@keyframes pulse { 0%,100% { opacity: 1; } 50% { opacity: 0.35; } }
.hero h1 {
  font-family: var(--display);
  font-size: 34px;
  font-weight: 700;
  letter-spacing: -0.02em;
  margin: 0 0 8px;
  color: var(--text);
}
.hero p { margin: 0; color: var(--text-dim); font-size: 15px; max-width: 560px; line-height: 1.6; }

/* ===== Stat cards ===== */
.stats-strip {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 12px;
  margin-bottom: 32px;
}
.stat {
  background: var(--bg-panel);
  backdrop-filter: blur(10px);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 16px 18px;
  transition: border-color 0.15s ease, transform 0.15s ease;
}
.stat:hover { border-color: var(--cyan-dim); transform: translateY(-2px); }
.stat .num { font-family: var(--display); font-size: 26px; font-weight: 700; line-height: 1; color: var(--text); }
.stat .num.c-cyan { color: var(--cyan); }
.stat .num.c-amber { color: var(--amber); }
.stat .num.c-danger { color: var(--danger); }
.stat .label { font-family: var(--mono); font-size: 10.5px; text-transform: uppercase; letter-spacing: 0.06em; color: var(--text-dim); margin-top: 9px; }

/* ===== Search ===== */
.search-bar { position: relative; margin-bottom: 20px; }
.search-bar svg { position: absolute; left: 14px; top: 50%; transform: translateY(-50%); color: var(--text-dim); pointer-events: none; }
#search-input {
  width: 100%;
  background: var(--bg-input);
  border: 1px solid var(--border);
  border-radius: 9px;
  padding: 12px 14px 12px 42px;
  color: var(--text);
  font-family: var(--sans);
  font-size: 14px;
  outline: none;
  transition: border-color 0.2s ease, box-shadow 0.2s ease;
}
#search-input::placeholder { color: #3a4453; }
#search-input:focus { border-color: var(--cyan-dim); box-shadow: 0 0 0 3px rgba(94,234,207,0.08); }

/* ===== Announcements ===== */
.ann {
  display: flex; gap: 12px;
  background: rgba(94,234,207,0.05);
  border: 1px solid var(--cyan-dim);
  border-radius: 11px;
  padding: 14px 16px;
  margin-bottom: 12px;
}
.ann .ann-ico { color: var(--cyan); flex-shrink: 0; margin-top: 1px; }
.ann b { color: var(--cyan); font-family: var(--display); font-size: 14px; }
.ann p { margin: 3px 0 0; color: #b5bfce; font-size: 13px; line-height: 1.55; }

/* ===== Problems table ===== */
table {
  width: 100%;
  border-collapse: collapse;
  background: var(--bg-panel);
  backdrop-filter: blur(10px);
  border: 1px solid var(--border);
  border-radius: 12px;
  overflow: hidden;
}
th, td { text-align: left; padding: 13px 18px; border-bottom: 1px solid var(--border-soft); }
tr:last-child td { border-bottom: none; }
th {
  color: var(--text-dim);
  font-weight: 600;
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  background: var(--bg-panel-hover);
  font-family: var(--mono);
}
tbody tr { transition: background 0.15s ease; }
tbody tr:hover { background: var(--bg-panel-hover); }
td.col-id { font-family: var(--mono); color: var(--text-dim); font-size: 13px; width: 60px; }
td.col-title { font-weight: 500; }
td.col-title a { color: var(--text); text-decoration: none; }
td.col-title a:hover { color: var(--cyan); }
.solve-link {
  color: var(--cyan);
  text-decoration: none;
  font-weight: 600;
  font-size: 13px;
  font-family: var(--mono);
  display: inline-flex; align-items: center; gap: 5px;
}
.solve-link:hover { gap: 9px; }

.badge {
  font-family: var(--mono);
  padding: 3px 10px;
  border-radius: 5px;
  font-size: 11px;
  font-weight: 600;
  border: 1px solid;
  text-transform: lowercase;
}
.badge-easy   { background: rgba(94,234,207,0.1); color: var(--cyan);   border-color: var(--cyan-dim); }
.badge-medium { background: rgba(240,179,41,0.1); color: var(--amber); border-color: #6b5620; }
.badge-hard   { background: rgba(239,106,90,0.1); color: var(--danger); border-color: #6b2530; }

.muted-row { color: var(--text-dim); font-family: var(--mono); font-size: 13px; }

/* ===== Pagination ===== */
#pagination { display: flex; justify-content: center; align-items: center; gap: 8px; margin-top: 22px; font-family: var(--mono); font-size: 13px; }
.page-btn {
  background: var(--bg-panel);
  border: 1px solid var(--border);
  color: var(--text);
  padding: 7px 14px;
  border-radius: 7px;
  cursor: pointer;
  font-family: var(--mono);
  font-size: 12px;
  transition: all 0.15s ease;
}
.page-btn:hover:not(:disabled) { border-color: var(--cyan-dim); color: var(--cyan); }
.page-btn:disabled { opacity: 0.35; cursor: not-allowed; }
#pagination .page-info { color: var(--text-dim); padding: 0 6px; }

/* ===== Trang giải bài (IDE 2 cột) ===== */
main.solve { max-width: 1240px; }
.back-link {
  display: inline-flex; align-items: center; gap: 6px;
  color: var(--text-dim); text-decoration: none; font-family: var(--mono);
  font-size: 12.5px; margin-bottom: 18px; transition: color 0.15s ease;
}
.back-link:hover { color: var(--cyan); }

.solve-grid { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1.05fr); gap: 20px; align-items: start; }

.panel {
  background: var(--bg-panel);
  backdrop-filter: blur(10px);
  border: 1px solid var(--border);
  border-radius: 14px;
  overflow: hidden;
}
.panel-head {
  display: flex; align-items: center; justify-content: space-between;
  padding: 12px 18px;
  border-bottom: 1px solid var(--border);
  background: var(--bg-panel-hover);
}
.panel-head .title { font-family: var(--mono); font-size: 12px; text-transform: uppercase; letter-spacing: 0.08em; color: var(--text-dim); display: flex; align-items: center; gap: 8px; }
.dots { display: inline-flex; gap: 5px; }
.dots i { width: 9px; height: 9px; border-radius: 50%; display: inline-block; }
.dots i:nth-child(1) { background: #ef6a5a; }
.dots i:nth-child(2) { background: #f0b429; }
.dots i:nth-child(3) { background: #5eeacf; }

/* Cột đề bài */
.statement-body { padding: 22px 24px 26px; }
#problem-title {
  font-family: var(--display);
  font-size: 24px; font-weight: 700; letter-spacing: -0.01em;
  color: var(--text); margin: 0 0 12px;
}
.limits { display: flex; gap: 10px; margin-bottom: 20px; flex-wrap: wrap; }
.limit-chip {
  font-family: var(--mono); font-size: 11.5px; color: var(--text-dim);
  background: var(--bg-input); border: 1px solid var(--border);
  padding: 6px 11px; border-radius: 7px;
}
.limit-chip b { color: var(--cyan); font-weight: 600; }
.limit-chip.diff-easy b { color: var(--cyan); }
.limit-chip.diff-medium b { color: var(--amber); }
.limit-chip.diff-hard b { color: var(--danger); }

.markdown-body { line-height: 1.72; color: #b5bfce; font-size: 14.5px; }
.markdown-body > *:first-child { margin-top: 0; }
.markdown-body h1, .markdown-body h2, .markdown-body h3 {
  font-family: var(--display); color: var(--text); margin: 22px 0 8px; line-height: 1.3;
}
.markdown-body h1 { font-size: 20px; }
.markdown-body h2 { font-size: 16px; }
.markdown-body h3 { font-size: 14px; }
.markdown-body p { margin: 0 0 12px; }
.markdown-body code { background: var(--bg-input); padding: 2px 6px; border-radius: 5px; font-family: var(--mono); font-size: 12.5px; color: var(--cyan); }
.markdown-body pre { background: var(--bg-input); border: 1px solid var(--border); border-radius: 9px; padding: 14px; overflow-x: auto; margin: 0 0 14px; }
.markdown-body pre code { background: none; padding: 0; color: var(--text); font-size: 12.5px; }
.markdown-body ul, .markdown-body ol { padding-left: 22px; margin: 0 0 12px; }
.markdown-body li { margin-bottom: 5px; }

/* Cột editor */
.editor-panel { position: sticky; top: 88px; }
.lang-pill { font-family: var(--mono); font-size: 11px; color: var(--cyan); background: rgba(94,234,207,0.08); border: 1px solid var(--cyan-dim); padding: 4px 10px; border-radius: 6px; }
#code-editor {
  width: 100%;
  display: block;
  font-family: var(--mono);
  font-size: 13.5px;
  line-height: 1.65;
  tab-size: 2;
  background: var(--bg-input);
  color: var(--text);
  border: none;
  padding: 16px 18px;
  resize: vertical;
  min-height: 380px;
  outline: none;
}
#code-editor::placeholder { color: #37404d; }
.editor-foot { display: flex; align-items: center; justify-content: space-between; padding: 14px 18px; border-top: 1px solid var(--border); gap: 12px; }
.editor-hint { font-family: var(--mono); font-size: 11px; color: var(--text-dim); }
#btn-submit {
  padding: 11px 26px;
  background: var(--cyan);
  color: #06110d;
  border: none;
  border-radius: 8px;
  font-weight: 700;
  font-size: 14px;
  font-family: var(--display);
  cursor: pointer;
  display: inline-flex; align-items: center; gap: 8px;
  transition: transform 0.15s ease, box-shadow 0.25s ease, opacity 0.15s ease;
}
#btn-submit:hover:not(:disabled) { box-shadow: 0 8px 24px -6px rgba(94,234,207,0.45); transform: translateY(-1px); }
#btn-submit:active { transform: translateY(0); }
#btn-submit:disabled { opacity: 0.6; cursor: not-allowed; }

#result-box { margin-top: 16px; }
.result-body { padding: 18px; }
.result-head-status { display: flex; align-items: center; justify-content: space-between; margin-bottom: 12px; flex-wrap: wrap; gap: 10px; }
.status-ac, .status-wa { display: inline-flex; align-items: center; gap: 9px; font-weight: 700; font-size: 17px; font-family: var(--display); }
.status-ac { color: var(--cyan); }
.status-wa { color: var(--danger); }
.status-ac::before { content: "✓"; }
.status-wa::before { content: "✕"; }
.score-pill { font-family: var(--mono); font-size: 13px; color: var(--text); background: var(--bg-input); border: 1px solid var(--border); padding: 5px 12px; border-radius: 7px; }
.metrics { display: flex; gap: 18px; font-family: var(--mono); font-size: 12.5px; color: var(--text-dim); flex-wrap: wrap; }
.metrics b { color: var(--text); font-weight: 600; }
.running { font-family: var(--mono); font-size: 13px; color: var(--text-dim); display: inline-flex; align-items: center; gap: 10px; }
.spinner { width: 14px; height: 14px; border: 2px solid var(--border); border-top-color: var(--cyan); border-radius: 50%; animation: spin 0.7s linear infinite; }
@keyframes spin { to { transform: rotate(360deg); } }

@media (max-width: 900px) {
  .solve-grid { grid-template-columns: 1fr; }
  .editor-panel { position: static; }
}

@media (prefers-reduced-motion: reduce) {
  * { animation: none !important; transition: none !important; }
}

@media (max-width: 640px) {
  nav { padding: 14px 18px; }
  main { padding: 28px 16px 60px; }
  .hero h1 { font-size: 26px; }
  .stats-strip { grid-template-columns: repeat(2, 1fr); }
  #nav-username span, nav button span { display: none; }
}

nav {
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  align-items: center;
}
nav h1 { justify-self: start; }
nav .nav-center { justify-self: center; display: flex; gap: 10px; }
#nav-auth { justify-self: end; display: flex; align-items: center; gap: 10px; }

.user-menu-trigger {
  display: none;
  align-items: center;
  gap: 6px;
  cursor: pointer;
  user-select: none;
}
.user-menu-trigger:hover { color: var(--cyan); }

.user-dropdown {
  position: absolute;
  top: calc(100% + 8px);
  right: 0;
  min-width: 180px;
  background: var(--bg-panel);
  backdrop-filter: blur(10px);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 6px;
  display: none;
  flex-direction: column;
  gap: 2px;
  z-index: 20;
  box-shadow: 0 12px 30px -8px rgba(0,0,0,0.6);
}
.user-dropdown.open { display: flex; }
.user-dropdown a { white-space: nowrap;
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 9px 12px;
  border-radius: 6px;
  color: var(--text);
  text-decoration: none;
  font-size: 13px;
  font-family: var(--sans);
  background: none;
  border: none;
  margin: 0;
}
.user-dropdown a:hover {
  background: var(--bg-panel-hover);
  color: var(--cyan);
  border-color: transparent;
}