:root {
  --bg: #0b0f14;
  --card: #121824;
  --muted: #99a3b3;
  --text: #e7eefc;
  --brand: #7aa2ff;
  --accent: #9be7ff;
  --danger: #ff7a7a;
  --ring: #2a3a55;
}

* {
  box-sizing: border-box
}

html,
body {
  height: 100%;
  background: radial-gradient(1200px 600px at 80% -10%, #122036 0%, transparent 60%),
    linear-gradient(180deg, #0b0f14 0%, #0b0f14 100%);
  color: var(--text);
  font-family: ui-sans-serif, system-ui, -apple-system, Segoe UI, Roboto, Helvetica, Arial, "Apple Color Emoji", "Segoe UI Emoji";
}

.container {
  max-width: 720px;
  margin: clamp(24px, 6vh, 64px) auto;
  padding: 0 16px;
}

h1 {
  font-size: clamp(1.6rem, 1.2rem + 2vw, 2.4rem);
  line-height: 1.1;
  margin: 8px 0 20px;
  letter-spacing: 0.2px;
}

.card {
  background: linear-gradient(180deg, rgba(255, 255, 255, 0.03), rgba(255, 255, 255, 0.02));
  border: 1px solid rgba(122, 162, 255, 0.15);
  border-radius: 16px;
  padding: 18px;
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.35);
  backdrop-filter: blur(6px);
}

.field {
  margin-bottom: 14px;
}

label {
  display: block;
  font-weight: 600;
  margin-bottom: 8px;
}

.input-row {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
}

input,
select {
  width: 100%;
  background: var(--card);
  color: var(--text);
  border: 1px solid var(--ring);
  border-radius: 12px;
  padding: 12px 12px;
  outline: none;
  transition: border-color .15s, box-shadow .15s;
}

input:focus,
select:focus {
  border-color: var(--brand);
  box-shadow: 0 0 0 3px rgba(122, 162, 255, 0.25);
}

select#unit {
  flex: 1;
  max-width: 120px;
}

.hint {
  color: var(--muted);
  font-size: 0.9rem;
  margin-top: 6px;
}

.btn {
  appearance: none;
  border: none;
  border-radius: 12px;
  padding: 12px 16px;
  font-weight: 700;
  cursor: pointer;
  background: linear-gradient(180deg, var(--brand), #597fe6);
  color: #0b1020;
  box-shadow: 0 10px 20px rgba(122, 162, 255, 0.25);
  transition: transform .06s ease, filter .15s ease;
  margin-right: 8px;
}

.btn:hover {
  filter: brightness(1.05)
}

.btn:active {
  transform: translateY(1px)
}

.btn-ghost {
  background: transparent;
  color: var(--text);
  border: 1px dashed var(--ring);
  box-shadow: none;
}

.error {
  min-height: 1.2em;
  color: var(--danger);
  font-weight: 600;
  margin-top: 10px;
}

.result {
  margin-top: 18px;
  text-align: center;
}

.result h2 {
  margin: 4px 0 8px;
  font-size: 1.2rem;
  color: var(--accent);
  letter-spacing: 0.3px;
}

.result-value {
  font-size: clamp(2rem, 1.5rem + 3vw, 3rem);
  font-weight: 800;
  margin: 8px 0;
}

.subtext {
  color: var(--muted);
  margin-top: 4px;
}

.footnote {
  color: var(--muted);
  font-size: 0.9rem;
  margin-top: 18px;
  text-align: center;
}

.top img {
  height: 40px;
  padding: 5px;
}

@media (max-width: 480px) {
  .card {
    padding: 14px;
  }

  .btn {
    width: 100%;
    margin: 6px 0;
  }

  .input-row {
    flex-direction: column;
  }

  select#unit {
    max-width: 100%;
  }

  .result-value {
    font-size: 2rem;
  }
}