:root {
  --bg: #0B1120;
  --panel: #121A2E;
  --panel-raised: #17213A;
  --border: #263452;
  --text: #E8ECF4;
  --text-muted: #7C8AA5;
  --amber: #FFB020;
  --cyan: #35D6C4;
  --green: #33C481;
  --red: #FF5D5D;

  --font-display: "Sora", sans-serif;
  --font-body: "Inter", sans-serif;
  --font-mono: "JetBrains Mono", monospace;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  background: radial-gradient(circle at 20% -10%, #16223f 0%, var(--bg) 55%);
  color: var(--text);
  font-family: var(--font-body);
  min-height: 100vh;
}

a { color: inherit; }

.scanline {
  position: fixed;
  inset: 0;
  pointer-events: none;
  background: repeating-linear-gradient(
    to bottom, rgba(255,255,255,0.015) 0px, rgba(255,255,255,0.015) 1px,
    transparent 1px, transparent 3px
  );
  z-index: 1;
}

/* ---------- topbar ---------- */
.topbar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 20px 32px;
  border-bottom: 1px solid var(--border);
}
.brand {
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 20px;
  text-decoration: none;
  color: var(--text);
  letter-spacing: 0.02em;
}
.brand-mark { color: var(--cyan); margin-right: 6px; }
.topnav { display: flex; align-items: center; gap: 20px; font-size: 14px; }
.topnav a { text-decoration: none; color: var(--text-muted); transition: color .15s; }
.topnav a:hover { color: var(--text); }
.nav-user { color: var(--amber); font-family: var(--font-mono); font-size: 13px; }
.nav-cta {
  background: var(--cyan);
  color: #062220 !important;
  padding: 8px 16px;
  border-radius: 6px;
  font-weight: 600;
}

/* ---------- flash ---------- */
.flash-stack { max-width: 720px; margin: 16px auto 0; padding: 0 24px; }
.flash {
  padding: 10px 14px;
  border-radius: 6px;
  font-size: 14px;
  margin-bottom: 8px;
  font-family: var(--font-mono);
}
.flash-error { background: rgba(255,93,93,0.12); color: var(--red); border: 1px solid rgba(255,93,93,0.3); }
.flash-success { background: rgba(51,196,129,0.12); color: var(--green); border: 1px solid rgba(51,196,129,0.3); }

.page { position: relative; z-index: 2; max-width: 960px; margin: 0 auto; padding: 48px 24px 80px; }

/* ---------- hero / landing ---------- */
.hero-eyebrow {
  font-family: var(--font-mono);
  color: var(--cyan);
  font-size: 13px;
  margin: 0 0 16px;
}
.hero-title {
  font-family: var(--font-display);
  font-size: clamp(36px, 6vw, 56px);
  font-weight: 800;
  line-height: 1.05;
  margin: 0 0 20px;
}
.accent-cyan { color: var(--cyan); }
.hero-sub { color: var(--text-muted); max-width: 560px; line-height: 1.6; font-size: 16px; }

.rack {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 20px;
  margin-top: 48px;
}
.rack-card {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 24px;
  position: relative;
  overflow: hidden;
}
.rack-card::before {
  content: "";
  position: absolute; inset: 0 0 auto 0; height: 3px;
}
.led-green::before { background: var(--green); }
.led-amber::before { background: var(--amber); }
.led-red::before { background: var(--red); }
.rack-led {
  width: 10px; height: 10px; border-radius: 50%;
  margin-bottom: 14px;
  box-shadow: 0 0 8px currentColor;
}
.led-green .rack-led { background: var(--green); color: var(--green); }
.led-amber .rack-led { background: var(--amber); color: var(--amber); }
.led-red .rack-led { background: var(--red); color: var(--red); }
.rack-label { font-family: var(--font-mono); font-weight: 700; letter-spacing: 0.08em; font-size: 14px; }
.rack-desc { color: var(--text-muted); font-size: 14px; margin: 10px 0 22px; line-height: 1.5; }
.rack-btn {
  display: inline-block;
  text-decoration: none;
  font-size: 14px;
  font-weight: 600;
  color: var(--text);
  border: 1px solid var(--border);
  padding: 8px 14px;
  border-radius: 6px;
  transition: border-color .15s, color .15s;
}
.rack-btn:hover { border-color: var(--cyan); color: var(--cyan); }

/* ---------- auth ---------- */
.auth-panel { max-width: 420px; margin: 0 auto; }
.auth-title { font-family: var(--font-display); font-size: 30px; margin: 0 0 28px; }
.auth-form { display: flex; flex-direction: column; gap: 16px; }
.auth-form label { font-size: 13px; color: var(--text-muted); display: flex; flex-direction: column; gap: 6px; }
.auth-form input {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 10px 12px;
  color: var(--text);
  font-family: var(--font-body);
  font-size: 15px;
}
.auth-form input:focus { outline: 2px solid var(--cyan); outline-offset: 1px; border-color: var(--cyan); }
.auth-alt { color: var(--text-muted); font-size: 14px; margin-top: 18px; }
.auth-alt a { color: var(--cyan); }

.btn-primary {
  background: var(--amber);
  color: #201200;
  border: none;
  padding: 12px 20px;
  border-radius: 6px;
  font-weight: 700;
  font-size: 15px;
  cursor: pointer;
  text-decoration: none;
  text-align: center;
  display: inline-block;
  transition: transform .1s;
}
.btn-primary:hover { transform: translateY(-1px); }
.btn-ghost {
  border: 1px solid var(--border);
  color: var(--text);
  padding: 12px 20px;
  border-radius: 6px;
  text-decoration: none;
  font-weight: 600;
  font-size: 15px;
}

/* ---------- quiz ---------- */
.quiz-wrap { max-width: 640px; margin: 0 auto; }
.quiz-hud {
  display: flex;
  justify-content: space-between;
  font-family: var(--font-mono);
  font-size: 13px;
  color: var(--text-muted);
  margin-bottom: 10px;
}
.hud-mode { color: var(--amber); font-weight: 700; }
.timer-track {
  height: 6px;
  background: var(--panel);
  border-radius: 4px;
  overflow: hidden;
  margin-bottom: 32px;
  border: 1px solid var(--border);
}
.timer-fill {
  height: 100%;
  width: 100%;
  background: var(--green);
  transition: width .2s linear, background-color .3s;
}

.packet-card {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 36px 32px;
  text-align: center;
  position: relative;
  margin-bottom: 24px;
}
.stamp-badge {
  position: absolute;
  top: 18px; right: 22px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.15em;
  color: var(--cyan);
  border: 1px solid var(--cyan);
  padding: 3px 8px;
  border-radius: 4px;
  transform: rotate(4deg);
}
.port-number {
  font-family: var(--font-mono);
  font-size: 64px;
  font-weight: 700;
  color: var(--text);
  line-height: 1;
}
.port-protocol {
  font-family: var(--font-mono);
  color: var(--text-muted);
  font-size: 13px;
  margin-top: 8px;
  letter-spacing: 0.1em;
}
.packet-question { color: var(--text-muted); margin-top: 20px; font-size: 15px; }

.options-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 14px;
}
.option-btn {
  background: var(--panel-raised);
  border: 1px solid var(--border);
  color: var(--text);
  padding: 16px 18px;
  border-radius: 8px;
  font-size: 15px;
  font-weight: 600;
  text-align: left;
  cursor: pointer;
  transition: border-color .15s, background .15s;
}
.option-btn:hover:not(:disabled) { border-color: var(--cyan); }
.option-btn.is-correct { border-color: var(--green); background: rgba(51,196,129,0.12); }
.option-btn.is-wrong { border-color: var(--red); background: rgba(255,93,93,0.12); }
.option-btn:disabled { cursor: default; opacity: 0.85; }

.feedback-panel, .result-panel {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 24px;
  margin-top: 24px;
  text-align: center;
}
.feedback-verdict { font-family: var(--font-display); font-weight: 700; font-size: 20px; margin: 0 0 8px; }
.feedback-explain { color: var(--text-muted); line-height: 1.6; margin-bottom: 20px; }

.result-score { font-family: var(--font-mono); font-size: 48px; margin: 4px 0; color: var(--amber); }
.result-sub { color: var(--text-muted); margin-bottom: 24px; }
.result-actions { display: flex; gap: 12px; justify-content: center; flex-wrap: wrap; }

/* ---------- history ---------- */
.history-wrap { max-width: 640px; margin: 0 auto; }
.history-table { width: 100%; border-collapse: collapse; font-size: 14px; margin-top: 20px; }
.history-table th {
  text-align: left; color: var(--text-muted); font-weight: 600;
  border-bottom: 1px solid var(--border); padding: 10px 8px; font-size: 12px;
  letter-spacing: 0.05em; text-transform: uppercase;
}
.history-table td { padding: 12px 8px; border-bottom: 1px solid var(--border); font-family: var(--font-mono); }
.mode-easy { color: var(--green); }
.mode-intermediate { color: var(--amber); }
.mode-advanced { color: var(--red); }
.empty-state { color: var(--text-muted); }
.empty-state a { color: var(--cyan); }

.footer {
  text-align: center;
  color: var(--text-muted);
  font-size: 12px;
  padding: 24px;
  font-family: var(--font-mono);
}

@media (max-width: 520px) {
  .options-grid { grid-template-columns: 1fr; }
  .port-number { font-size: 48px; }
}

@media (prefers-reduced-motion: reduce) {
  .timer-fill { transition: none; }
  .btn-primary:hover { transform: none; }
}