:root {
  --bg-primary: #0a0a0f;
  --bg-secondary: #14141f;
  --bg-tertiary: #1e1e2e;
  --text-primary: #ffffff;
  --text-secondary: #a0a0b0;
  --text-muted: #606070;
  --accent: #00d4ff;
  --accent-secondary: #00ff88;
  --danger: #ff4466;
  --focus-ring: #00d4ff;
  --focus-glow: rgba(0, 212, 255, 0.4);
  --radius-md: 12px;
}

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

html, body {
  width: 600px; height: 600px; overflow: hidden;
  background: #000;
  color: var(--text-primary);
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  -webkit-font-smoothing: antialiased;
}

#app { width: 100%; height: 100%; position: relative; }

.screen {
  width: 100%; height: 100%; position: absolute; top: 0; left: 0;
  display: flex; flex-direction: column;
}
.screen.hidden { display: none; }
.hidden { display: none !important; }

.focusable {
  transition: all 0.15s ease;
  border: 2px solid transparent;
  cursor: pointer; outline: none;
}
.focusable:focus {
  border-color: var(--focus-ring);
  box-shadow: 0 0 20px var(--focus-glow);
}

/* ---- Header ---- */
.hdr { padding: 22px 24px 14px; }
.hdr h1 {
  font-size: 36px; font-weight: 700; letter-spacing: 0.5px;
  background: linear-gradient(90deg, var(--accent), var(--accent-secondary));
  -webkit-background-clip: text; background-clip: text;
  -webkit-text-fill-color: transparent;
}
.hdr .sub { color: var(--text-secondary); font-size: 16px; margin-top: 4px; }

.hdr.bar {
  display: flex; align-items: center; gap: 14px;
  padding: 16px 20px;
  border-bottom: 1px solid var(--bg-tertiary);
}
.hdr.bar h2 { font-size: 24px; font-weight: 600; }

.back {
  width: 48px; height: 48px; flex: 0 0 48px;
  background: var(--bg-tertiary); color: var(--text-primary);
  border-radius: var(--radius-md);
  font-size: 30px; line-height: 1; font-weight: 700;
  display: flex; align-items: center; justify-content: center;
}

/* ---- Home menu ---- */
.menu {
  flex: 1; display: flex; flex-direction: column;
  gap: 16px; padding: 8px 24px; justify-content: center;
}
.card-btn {
  background: var(--bg-secondary); color: var(--text-primary);
  border-radius: var(--radius-md);
  padding: 18px 22px; min-height: 96px;
  display: flex; flex-direction: column; gap: 8px; text-align: left;
}
.card-btn .big {
  font-size: 26px; font-weight: 700; color: var(--accent);
  letter-spacing: 1px;
}
.card-btn .big.sym-row { letter-spacing: 6px; }
.card-btn .lbl { font-size: 16px; color: var(--text-secondary); }

.hint {
  padding: 16px 24px 22px; color: var(--text-muted);
  font-size: 14px; text-align: center;
}

/* ---- Result panel ---- */
.result {
  flex: 1; display: flex; flex-direction: column;
  align-items: center; justify-content: center;
  gap: 10px; padding: 16px 24px; overflow: hidden;
}
.result .dec {
  font-size: 52px; font-weight: 700;
  font-variant-numeric: tabular-nums;
}
.result .rom {
  font-size: 50px; font-weight: 700; letter-spacing: 3px;
  color: var(--accent); text-align: center;
  line-height: 1.1; overflow-wrap: anywhere; max-width: 100%;
}
.result .rom.bad { color: var(--danger); letter-spacing: 1px; font-size: 40px; }
.result .arrow { font-size: 24px; color: var(--text-muted); }

/* ---- Steppers (dec -> rom) ---- */
.steppers {
  display: grid; grid-template-columns: repeat(4, 1fr);
  gap: 10px; padding: 0 20px;
}
.step {
  height: 74px; border-radius: var(--radius-md);
  font-size: 19px; font-weight: 700;
  background: var(--bg-secondary); color: var(--text-primary);
  font-variant-numeric: tabular-nums;
}
.step.minus { color: var(--danger); }
.step.plus { color: var(--accent-secondary); }

/* ---- Symbols (rom -> dec) ---- */
.symbols {
  display: grid; grid-template-columns: repeat(4, 1fr);
  gap: 10px; padding: 0 20px;
}
.sym {
  height: 74px; border-radius: var(--radius-md);
  background: var(--bg-secondary); color: var(--text-primary);
  font-size: 26px; font-weight: 700;
  display: flex; flex-direction: column; align-items: center; justify-content: center;
}
.sym small { font-size: 12px; color: var(--text-secondary); font-weight: 500; margin-top: 2px; }

/* ---- Action row ---- */
.actions {
  display: flex; gap: 12px; padding: 14px 20px 0; justify-content: center;
}
.minor {
  flex: 1; min-height: 56px; border-radius: var(--radius-md);
  background: var(--bg-tertiary); color: var(--text-primary);
  font-size: 17px; font-weight: 600;
}
.minor.wide { margin: 16px 20px 20px; flex: none; }

.note {
  padding: 14px 24px 22px; text-align: center;
  font-size: 15px; color: var(--text-secondary); min-height: 24px;
}
.note.ok { color: var(--accent-secondary); }
.note.err { color: var(--danger); }

/* ---- Reference ---- */
.ref-grid {
  flex: 1; display: grid; grid-template-columns: 1fr 1fr;
  gap: 16px; padding: 20px 24px; overflow-y: auto;
}
.ref-col h3 {
  font-size: 16px; color: var(--text-secondary);
  margin-bottom: 10px; text-transform: uppercase; letter-spacing: 1px;
}
table.ref { width: 100%; border-collapse: collapse; }
table.ref td {
  padding: 11px 12px; font-size: 22px; font-weight: 600;
  border-bottom: 1px solid var(--bg-tertiary);
  font-variant-numeric: tabular-nums;
}
table.ref td:first-child { color: var(--accent); letter-spacing: 2px; }
table.ref td:last-child { text-align: right; color: var(--text-secondary); }