/* === Variables === */
:root {
  --primary: #0b1f3a;
  --primary-light: #16345f;
  --background: #ffffff;
  --surface: #f8f9fa;
  --text: #111111;
  --muted: #6c757d;
  --border: #e5e7eb;
  --shadow: rgba(0,0,0,0.05);
}

[data-theme="dark"] {
  --background: #081120;
  --surface: #0f1c2e;
  --text: #ffffff;
  --muted: #b0b7c3;
  --border: rgba(255,255,255,0.08);
  --shadow: rgba(0,0,0,0.3);
}

/* === Base === */
*, *::before, *::after { box-sizing: border-box; }

body {
  font-family: 'Inter', system-ui, sans-serif;
  font-size: 15px;
  line-height: 1.6;
  color: var(--text);
  background-color: var(--background);
  margin: 0;
  transition: background-color 0.25s ease, color 0.25s ease;
}

/* === Layout === */
.container-xl {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 24px;
}

/* === Navbar === */
.navbar {
  height: 60px;
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  z-index: 100;
  display: flex;
  align-items: center;
  transition: background-color 0.25s ease, border-color 0.25s ease;
}
.navbar .container-xl {
  display: flex;
  align-items: center;
  justify-content: space-between;
  width: 100%;
}
.navbar-brand { text-decoration: none; }
.brand-text { font-weight: 700; color: var(--primary); }
[data-theme="dark"] .brand-text { color: #ffffff; }
.brand-dot { color: var(--primary); font-weight: 700; }
[data-theme="dark"] .brand-dot { color: #ffffff; }
.brand-tools { font-weight: 400; color: var(--muted); }
.nav-right { display: flex; align-items: center; gap: 16px; }
.nav-back { font-size: 14px; color: var(--muted); text-decoration: none; transition: color 0.2s; }
.nav-back:hover { color: var(--primary); }
[data-theme="dark"] .nav-back:hover { color: #ffffff; }
.theme-toggle {
  background: none;
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 6px 10px;
  cursor: pointer;
  font-size: 14px;
  transition: border-color 0.2s;
}
.theme-toggle:hover { border-color: var(--primary); }

/* === Tool Header === */
.tool-header { padding: 40px 0 24px; }
.tool-title { font-size: 28px; font-weight: 700; color: var(--primary); margin: 0; line-height: 1.2; }
[data-theme="dark"] .tool-title { color: #ffffff; }
.tool-description { font-size: 15px; color: var(--muted); margin-top: 6px; margin-bottom: 0; }

/* === Tool Main === */
.tool-main { padding: 0 0 80px; }

/* === Tool Card === */
.tool-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 24px;
  box-shadow: 0 2px 8px var(--shadow);
  max-width: 640px;
  margin: 0 auto;
  transition: background-color 0.25s ease, border-color 0.25s ease;
}

/* === Form Fields === */
.field-group { margin-bottom: 16px; }

.field-label {
  display: block;
  font-size: 14px;
  font-weight: 600;
  color: var(--text);
  margin-bottom: 6px;
}

.field-input,
.field-select {
  width: 100%;
  background: var(--background);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 10px 14px;
  color: var(--text);
  font-family: inherit;
  font-size: 15px;
  height: 44px;
  transition: border-color 0.2s;
  appearance: none;
  -webkit-appearance: none;
}
.field-input:focus,
.field-select:focus {
  outline: 2px solid var(--primary);
  outline-offset: 1px;
  border-color: var(--primary);
}

.field-select {
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 24 24' fill='none' stroke='%236c757d' stroke-width='2'%3E%3Cpath d='M6 9l6 6 6-6'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 12px center;
  padding-right: 36px;
  cursor: pointer;
}

.field-error {
  font-size: 13px;
  color: #dc3545;
  margin-top: 4px;
}

/* === Units Row === */
.units-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
  margin-bottom: 16px;
}

/* === Buttons === */
.btn-row {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  margin-bottom: 20px;
}

.btn {
  padding: 10px 24px;
  border-radius: 6px;
  font-size: 14px;
  font-weight: 500;
  font-family: inherit;
  cursor: pointer;
  border: none;
  min-height: 44px;
  transition: background-color 0.2s, color 0.2s, border-color 0.2s;
}

.btn-primary-ct {
  background-color: var(--primary);
  color: #ffffff;
  border: 1px solid var(--primary);
}
.btn-primary-ct:hover {
  background-color: var(--primary-light);
  border-color: var(--primary-light);
}

.btn-secondary-ct {
  background-color: var(--background);
  color: var(--primary);
  border: 1px solid var(--border);
}
[data-theme="dark"] .btn-secondary-ct { color: #ffffff; }
.btn-secondary-ct:hover {
  background-color: var(--primary);
  color: #ffffff;
  border-color: var(--primary);
}

/* === Result Area === */
.result-area {
  background: var(--background);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 24px 20px;
  min-height: 96px;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: border-color 0.25s ease, background-color 0.25s ease;
}

.result-placeholder {
  color: var(--muted);
  font-size: 14px;
}

.result-content {
  text-align: center;
  width: 100%;
}

.result-value {
  font-size: 32px;
  font-weight: 700;
  color: var(--primary);
  line-height: 1.2;
  margin-bottom: 6px;
  word-break: break-all;
}
[data-theme="dark"] .result-value { color: #ffffff; }

.result-formula {
  font-size: 13px;
  color: var(--muted);
}

/* === Footer === */
.site-footer { padding: 24px 0; border-top: 1px solid var(--border); }
.footer-text { font-size: 13px; color: var(--muted); text-align: center; margin: 0; }
.footer-text a { color: var(--primary); text-decoration: none; }
[data-theme="dark"] .footer-text a { color: #ffffff; }
.footer-text a:hover { text-decoration: underline; }

/* === Responsive === */
@media (max-width: 575px) {
  .tool-card { padding: 16px; }
  .tool-title { font-size: 22px; }
  .units-row { grid-template-columns: 1fr; }
  .btn { width: 100%; }
  .result-value { font-size: 26px; }
}