:root {
  --bg: #0a0e14;
  --bg-panel: #10161f;
  --bg-raised: #161d29;
  --border: #232c3a;
  --green: #39ff88;
  --green-dim: #1f8a4c;
  --blue: #58a6ff;
  --red: #ff5f6d;
  --yellow: #ffd166;
  --text: #e6edf3;
  --text-dim: #8b949e;
  --font-mono: 'JetBrains Mono', ui-monospace, monospace;
  --font-display: 'Space Grotesk', sans-serif;
}

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

.bg-grid {
  position: fixed; inset: 0; z-index: 0; pointer-events: none;
  background-image:
    linear-gradient(rgba(57,255,136,0.035) 1px, transparent 1px),
    linear-gradient(90deg, rgba(57,255,136,0.035) 1px, transparent 1px);
  background-size: 34px 34px;
  mask-image: radial-gradient(ellipse at 50% 0%, black 0%, transparent 75%);
}

header.topbar {
  position: relative; z-index: 1;
  display: flex; align-items: center; justify-content: space-between;
  gap: 16px; padding: 14px 24px;
  border-bottom: 1px solid var(--border);
  background: linear-gradient(180deg, #0d1420, #0a0e14);
  flex-wrap: wrap;
}
.brand { display: flex; align-items: center; gap: 12px; }
.brand-glyph {
  font-weight: 800; font-size: 22px; color: var(--green);
  background: var(--bg-raised); border: 1px solid var(--green-dim);
  padding: 6px 10px; border-radius: 6px;
  text-shadow: 0 0 12px rgba(57,255,136,0.6);
}
.brand-text { display: flex; flex-direction: column; line-height: 1.25; }
.brand-title { font-family: var(--font-display); font-weight: 700; letter-spacing: 0.5px; font-size: 17px; }
.brand-title .accent { color: var(--green); }
.brand-sub { font-size: 11px; color: var(--text-dim); }

.stats { display: flex; gap: 18px; }
.stat { display: flex; flex-direction: column; align-items: center; min-width: 60px; }
.stat-label { font-size: 10px; letter-spacing: 1px; color: var(--text-dim); text-transform: uppercase; }
.stat-value { font-size: 20px; font-weight: 700; color: var(--green); text-shadow: 0 0 10px rgba(57,255,136,0.4); }

.topbar-actions { display: flex; gap: 8px; flex-wrap: wrap; }
.btn-outline, .btn-primary, .btn-ghost, .btn-small {
  font-family: var(--font-mono); font-size: 12.5px; cursor: pointer;
  border-radius: 6px; padding: 8px 12px; transition: all 0.15s ease;
}
.btn-outline { background: transparent; border: 1px solid var(--border); color: var(--text); }
.btn-outline:hover { border-color: var(--green-dim); color: var(--green); }
.btn-ghost { background: transparent; border: 1px solid transparent; color: var(--text-dim); }
.btn-ghost:hover { color: var(--red); }
.btn-primary {
  background: linear-gradient(180deg, #2ee673, #1f8a4c); border: 1px solid #1f8a4c;
  color: #04140a; font-weight: 700;
}
.btn-primary:hover { filter: brightness(1.1); }
.btn-small {
  background: var(--bg-raised); border: 1px solid var(--border); color: var(--text);
}
.btn-small:disabled { opacity: 0.4; cursor: not-allowed; }
.btn-small:not(:disabled):hover { border-color: var(--green-dim); color: var(--green); }

.level-tabs {
  position: relative; z-index: 1;
  display: flex; gap: 6px; padding: 10px 24px; overflow-x: auto;
  border-bottom: 1px solid var(--border); background: #0c121b;
}
.level-tab {
  font-family: var(--font-mono); font-size: 12px; white-space: nowrap;
  background: transparent; border: 1px solid var(--border); color: var(--text-dim);
  padding: 6px 12px; border-radius: 999px; cursor: pointer; transition: all 0.15s ease;
}
.level-tab:hover { color: var(--text); }
.level-tab.active { background: rgba(57,255,136,0.1); border-color: var(--green-dim); color: var(--green); }

.layout {
  position: relative; z-index: 1;
  display: grid; grid-template-columns: 1fr 1fr; gap: 18px;
  padding: 20px 24px; max-width: 1400px; margin: 0 auto;
}
@media (max-width: 900px) { .layout { grid-template-columns: 1fr; } }

.panel {
  background: var(--bg-panel); border: 1px solid var(--border); border-radius: 10px;
  display: flex; flex-direction: column; overflow: hidden;
}
.challenge-panel { padding: 18px; gap: 12px; }
.panel-head { display: flex; align-items: center; justify-content: space-between; }
.badge {
  font-size: 11px; padding: 4px 10px; border-radius: 999px;
  background: rgba(88,166,255,0.12); color: var(--blue); border: 1px solid rgba(88,166,255,0.3);
}
.stars { color: var(--yellow); font-size: 14px; letter-spacing: 2px; }
.prompt-text { font-size: 16px; line-height: 1.55; color: var(--text); min-height: 60px; }
.hint-box {
  display: none; font-size: 13px; color: var(--yellow); background: rgba(255,209,102,0.08);
  border: 1px solid rgba(255,209,102,0.25); border-radius: 8px; padding: 10px 12px;
}
.hint-box.visible { display: block; }
.feedback-banner { min-height: 20px; font-size: 13px; border-radius: 8px; padding: 0; transition: all 0.15s ease; }
.feedback-banner.correct { color: var(--green); background: rgba(57,255,136,0.08); border: 1px solid rgba(57,255,136,0.25); padding: 10px 12px; }
.feedback-banner.incorrect { color: var(--red); background: rgba(255,95,109,0.08); border: 1px solid rgba(255,95,109,0.25); padding: 10px 12px; }
.challenge-actions { display: flex; gap: 8px; flex-wrap: wrap; margin-top: 4px; }
.progress-wrap { margin-top: 8px; }
.progress-bar { height: 8px; background: var(--bg-raised); border-radius: 999px; overflow: hidden; border: 1px solid var(--border); }
.progress-bar-fill { height: 100%; width: 0%; background: linear-gradient(90deg, var(--green-dim), var(--green)); transition: width 0.3s ease; }
.progress-text { font-size: 11px; color: var(--text-dim); display: block; margin-top: 6px; }
.tips { font-size: 11px; color: var(--text-dim); line-height: 1.6; border-top: 1px solid var(--border); padding-top: 10px; margin-top: auto; }
.tips code { background: var(--bg-raised); padding: 1px 5px; border-radius: 4px; color: var(--blue); }

.terminal-panel { min-height: 520px; }
.term-titlebar {
  display: flex; align-items: center; gap: 7px; padding: 9px 12px;
  background: #0d1420; border-bottom: 1px solid var(--border);
}
.dot { width: 10px; height: 10px; border-radius: 50%; }
.dot.red { background: #ff5f56; } .dot.yellow { background: #ffbd2e; } .dot.green { background: #27c93f; }
.term-title { margin-left: 8px; font-size: 11px; color: var(--text-dim); }
.term-body {
  flex: 1; padding: 14px; overflow-y: auto; font-size: 13px; line-height: 1.5;
  background: #0a0e14; min-height: 380px; max-height: 460px;
}
.term-line { white-space: pre-wrap; word-break: break-word; color: var(--text); }
.term-cmd-echo { color: var(--blue); }
.term-error { color: var(--red); }
.term-hint-line { color: var(--text-dim); }
.term-inputline {
  display: flex; align-items: center; gap: 8px; padding: 10px 14px;
  border-top: 1px solid var(--border); background: #0d1420;
}
.term-prompt { color: var(--green); font-size: 13px; white-space: nowrap; }
#term-input {
  flex: 1; background: transparent; border: none; outline: none;
  color: var(--text); font-family: var(--font-mono); font-size: 13px;
}

.footer {
  position: relative; z-index: 1; text-align: center; padding: 18px;
  color: var(--text-dim); font-size: 11px; border-top: 1px solid var(--border);
}

/* modals */
.modal-overlay {
  display: none; position: fixed; inset: 0; z-index: 50; background: rgba(4,6,10,0.75);
  align-items: center; justify-content: center; padding: 20px;
}
.modal-overlay.open { display: flex; }
.modal {
  background: var(--bg-panel); border: 1px solid var(--border); border-radius: 12px;
  padding: 22px; max-width: 520px; width: 100%; max-height: 82vh; overflow-y: auto;
}
.modal-wide { max-width: 760px; }
.modal-header { display: flex; align-items: center; justify-content: space-between; }
.modal-header h2 { font-family: var(--font-display); font-size: 18px; margin: 0; }
.modal-close { background: transparent; border: none; color: var(--text-dim); font-size: 16px; cursor: pointer; }
.modal-close:hover { color: var(--red); }
.modal-sub { color: var(--text-dim); font-size: 12.5px; margin: 8px 0 4px; }
.modal-hint { font-size: 12.5px; color: var(--text-dim); line-height: 1.6; }

.interview-list { display: flex; flex-direction: column; gap: 8px; margin-top: 12px; }
.interview-card {
  border: 1px solid var(--border); border-radius: 8px; padding: 12px; cursor: pointer;
  background: var(--bg-raised);
}
.interview-level {
  font-size: 10px; color: var(--blue); border: 1px solid rgba(88,166,255,0.3);
  border-radius: 999px; padding: 2px 8px; margin-right: 8px;
}
.interview-q { font-size: 13px; }
.interview-a { display: none; font-size: 12.5px; color: var(--text-dim); margin-top: 8px; line-height: 1.6; border-top: 1px dashed var(--border); padding-top: 8px; }
.interview-card.open .interview-a { display: block; }

.cert-list { display: flex; flex-direction: column; gap: 10px; margin-top: 12px; }
.cert-row {
  display: flex; align-items: center; justify-content: space-between;
  border: 1px solid var(--border); border-radius: 8px; padding: 12px; background: var(--bg-raised);
}
.cert-title { font-size: 13px; font-weight: 700; }
.cert-sub { font-size: 11px; color: var(--text-dim); margin-top: 3px; }