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

:root {
  --bg: #eff2ee;
  --bg-deep: #e3e8e1;
  --surface: rgba(250, 252, 249, 0.82);
  --surface-strong: #ffffff;
  --surface-muted: #f3f6f2;

  --text: #1f2a24;
  --text-secondary: #66756b;
  --text-tertiary: #93a197;

  --border: rgba(31, 42, 36, 0.10);
  --border-strong: rgba(31, 42, 36, 0.16);

  --accent: #2f6b57;
  --accent-hover: #275847;
  --accent-soft: rgba(47, 107, 87, 0.12);

  --radius: 16px;
  --radius-lg: 26px;

  --font: "Hiragino Sans", "Noto Sans JP", -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif
  --mono: "SFMono-Regular", "Consolas", monospace;

  --shadow-sm: 0 8px 24px rgba(38, 54, 46, 0.07);
  --shadow-md: 0 24px 60px rgba(38, 54, 46, 0.10);
}

body {
  font-family: var(--font);
  color: var(--text);
  min-height: 100vh;
  padding: 32px 20px;
  background:
    url('/static/images/miku2_by_mitsura169.png') no-repeat left 0px top 20px / 400px auto,
    url('/static/images/miku1_by_mitsura169.png') no-repeat right 60px bottom 20px / 350px auto,
    radial-gradient(circle at top left, #fbfdfb 0%, transparent 30%),
    radial-gradient(circle at bottom right, #dbe5de 0%, transparent 32%),
    linear-gradient(180deg, var(--bg) 0%, var(--bg-deep) 100%);
  -webkit-font-smoothing: antialiased;
  position: relative;
  overflow-x: hidden;
}

.container {
  position: relative;
  width: 640px;
  max-width: 100%;
  margin: 0 auto;
  z-index: 1;
}

.header {
  text-align: center;
  margin-bottom: 30px;
}

.header h1 {
  font-size: 36px;
  line-height: 1.15;
  font-weight: 700;
  letter-spacing: -0.03em;
  margin-bottom: 10px;
}

.header p {
  font-size: 15px;
  line-height: 1.8;
  color: var(--text-secondary);
  max-width: 560px;
  margin: 0 auto;
}

.card,
.result-card,
.footer {
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
}

.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 30px;
  box-shadow: var(--shadow-md);
  margin-bottom: 16px;
}

.form-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 18px;
}

.form-group {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.form-group label {
  font-size: 12px;
  font-weight: 600;
  color: var(--text-secondary);
  letter-spacing: 0.04em;
}

.form-group input,
.form-group select {
  width: 100%;
  min-height: 54px;
  border-radius: 15px;
  border: 1px solid var(--border);
  background: var(--surface-muted);
  color: var(--text);
  font-size: 15px;
  font-family: var(--font);
  padding: 14px 16px;
  outline: none;
  transition: 0.22s ease;
  appearance: none;
}

.form-group input::placeholder {
  color: var(--text-tertiary);
}

.form-group input:hover,
.form-group select:hover {
  background: #f7faf6;
  border-color: var(--border-strong);
}

.form-group input:focus,
.form-group select:focus {
  background: #ffffff;
  border-color: var(--accent);
  box-shadow: 0 0 0 4px rgba(47, 107, 87, 0.12);
}

.select-wrapper {
  position: relative;
}

.select-wrapper::after {
  content: "";
  position: absolute;
  right: 16px;
  top: 50%;
  width: 8px;
  height: 8px;
  border-right: 1.8px solid var(--text-secondary);
  border-bottom: 1.8px solid var(--text-secondary);
  transform: translateY(-65%) rotate(45deg);
  pointer-events: none;
}

.divider {
  height: 1px;
  background: linear-gradient(90deg, transparent, var(--border-strong), transparent);
  margin: 26px 0 22px;
}

.btn {
  width: 100%;
  min-height: 56px;
  border: none;
  border-radius: 16px;
  background: linear-gradient(135deg, #2f6b57 0%, #275847 100%);
  color: #f8fcf9;
  font-size: 16px;
  font-weight: 700;
  letter-spacing: 0.01em;
  cursor: pointer;
  transition: 0.22s ease;
  box-shadow: 0 14px 32px rgba(47, 107, 87, 0.20);
}

.btn:hover {
  transform: translateY(-1px);
  box-shadow: 0 18px 38px rgba(47, 107, 87, 0.25);
}

.btn:active {
  transform: translateY(0);
}

.btn:disabled {
  opacity: 0.6;
  pointer-events: none;
}

.btn .spinner {
  display: inline-block;
  width: 14px;
  height: 14px;
  border: 2px solid rgba(255,255,255,0.32);
  border-top-color: #fff;
  border-radius: 50%;
  animation: spin 0.65s linear infinite;
  margin-right: 8px;
  vertical-align: -2px;
}

@keyframes spin {
  to { transform: rotate(360deg); }
}

.result-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  text-align: center;
  box-shadow: var(--shadow-md);
  opacity: 0;
  transform: translateY(10px);
  max-height: 0;
  overflow: hidden;
  transition: all 0.35s ease;
}

.result-card.visible {
  opacity: 1;
  transform: translateY(0);
  max-height: 220px;
  padding: 30px;
  margin-bottom: 16px;
}

.result-label {
  font-size: 12px;
  color: var(--text-secondary);
  margin-bottom: 12px;
  letter-spacing: 0.04em;
}

.result-value {
  font-family: var(--mono);
  font-size: 40px;
  font-weight: 700;
  color: #224b3d;
  letter-spacing: -0.03em;
}

.result-unit {
  font-size: 15px;
  color: var(--text-secondary);
  margin-left: 6px;
}

.error-msg {
  display: none;
  margin-top: 14px;
  border-radius: 14px;
  padding: 13px 14px;
  text-align: center;
  font-size: 14px;
  background: rgba(185, 28, 28, 0.06);
  color: #b42318;
  border: 1px solid rgba(185, 28, 28, 0.12);
}

.footer {
  background: rgba(250, 252, 249, 0.76);
  border: 1px solid var(--border);
  border-radius: 22px;
  padding: 22px;
  box-shadow: var(--shadow-sm);
  text-align: center;
}

.footer-description {
  font-size: 14px;
  line-height: 1.95;
  color: var(--text-secondary);
  margin-bottom: 16px;
}

.footer-credit {
  font-size: 12px;
  color: var(--text-tertiary);
  border-top: 1px solid var(--border);
  padding-top: 12px;
}

.footer-credit a {
  color: #275847;
  text-decoration: none;
}

.footer-credit a:hover {
  text-decoration: underline;
}

.footer-credit + .footer-credit {
  border-top: none;
  padding-top: 4px;
}

.lang-switch {
  display: inline-flex;
  gap: 6px;
  padding: 6px;
  margin-bottom: 18px;
  border: 1px solid var(--border);
  border-radius: 999px;
  background: rgba(250, 252, 249, 0.78);
  box-shadow: var(--shadow-sm);
}

.lang-btn {
  min-width: 74px;
  height: 38px;
  border: none;
  border-radius: 999px;
  background: transparent;
  color: var(--text-secondary);
  font-weight: 700;
  cursor: pointer;
  transition: 0.2s ease;
}

.lang-btn:hover {
  background: rgba(47, 107, 87, 0.08);
  color: var(--text);
}

.lang-btn.active {
  background: linear-gradient(135deg, #2f6b57 0%, #275847 100%);
  color: #fff;
}

@media (max-width: 640px) {
  body {
    padding: 20px 14px;
    align-items: flex-start;
  }

  .header h1 {
    font-size: 30px;
  }

  .card,
  .result-card.visible,
  .footer {
    padding: 20px;
  }

  .form-grid {
    grid-template-columns: 1fr;
    gap: 14px;
  }

  .result-value {
    font-size: 34px;
  }
}