/* ═══════════════════════════════════════════
   英文单复数转换 - 自定义样式
   ═══════════════════════════════════════════ */

:root {
  --bg: #FAFAF9; --bg-alt: #F5F5F4; --surface: #FFFFFF;
  --border: #E7E5E4; --border-strong: #D6D3D1;
  --text: #1E293B; --text-secondary: #52525B; --text-muted: #71717A;
  --primary: #4F46E5; --primary-hover: #4338CA;
  --primary-light: rgba(79, 70, 229, 0.08);
  --secondary: #F97316; --accent: #EC4899; --success: #059669;
  --radius: 10px; --radius-lg: 14px; --radius-xl: 20px;
}

* { margin: 0; padding: 0; box-sizing: border-box; }
html { scroll-behavior: smooth; }

body {
  font-family: 'Inter', 'Noto Sans SC', system-ui, sans-serif;
  background: var(--bg); color: var(--text);
  line-height: 1.6; min-height: 100vh;
  -webkit-font-smoothing: antialiased;
}

.toast {
  position: fixed; top: 24px; right: 24px;
  background: var(--text); color: var(--bg);
  padding: 10px 18px; border-radius: 100px;
  font-size: 14px; font-weight: 500;
  display: flex; align-items: center; gap: 8px;
  z-index: 1000;
  transform: translateX(calc(100% + 40px));
  transition: transform 0.3s cubic-bezier(0.34, 1.56, 0.64, 1);
  box-shadow: 0 4px 16px rgba(0,0,0,0.12);
}
.toast.show { transform: translateX(0); }
.toast-dot { width: 8px; height: 8px; background: var(--success); border-radius: 50%; }

.page { max-width: 960px; margin: 0 auto; padding: 0 32px; }

#header.scrolled {
  background: rgba(255,255,255,0.95);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  box-shadow: 0 2px 20px rgba(0,0,0,0.06);
}

.plural-section { padding: 24px 0 32px; }

.plural-panel {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.06);
  overflow: hidden;
  margin-bottom: 20px;
}
.plural-panel:hover { box-shadow: 0 8px 30px rgba(0,0,0,0.08); }
.plural-body { padding: 24px; }

.input-row {
  display: flex; gap: 12px; align-items: flex-end;
  margin-bottom: 20px;
}

.input-field {
  flex: 1; min-width: 0;
  padding: 14px 16px;
  background: var(--bg-alt);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  font-family: inherit; font-size: 17px; color: var(--text);
  transition: all 0.2s ease; outline: none;
}
.input-field:focus {
  border-color: var(--primary); background: var(--surface);
  box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.1);
}
.input-field::placeholder { color: #9CA3AF; }

.btn-group { display: flex; gap: 8px; }

.btn-primary {
  padding: 14px 24px;
  background: var(--primary); border: 1px solid transparent;
  border-radius: var(--radius);
  font-family: inherit; font-size: 15px; font-weight: 600;
  color: white; cursor: pointer;
  transition: background 0.15s ease, box-shadow 0.15s ease, transform 0.15s ease;
  box-shadow: 0 1px 3px rgba(0,0,0,0.06);
  white-space: nowrap;
}
.btn-primary:hover { background: var(--primary-hover); box-shadow: 0 4px 12px rgba(0,0,0,0.10); transform: translateY(-1px); }

.btn-secondary {
  padding: 14px 24px;
  background: var(--bg-alt); border: 1px solid var(--border);
  border-radius: var(--radius);
  font-family: inherit; font-size: 15px; font-weight: 500;
  color: var(--text-secondary); cursor: pointer;
  transition: all 0.15s ease; white-space: nowrap;
}
.btn-secondary:hover { border-color: var(--primary); color: var(--primary); background: var(--primary-light); }

.result-card {
  background: linear-gradient(135deg, rgba(139,92,246,0.06), rgba(236,72,153,0.04));
  border: 1px solid var(--border);
  border-radius: var(--radius-lg); padding: 24px;
  margin-top: 16px;
  text-align: center;
}
.result-word {
  font-size: 36px; font-weight: 700;
  color: var(--text);
  font-family: 'Inter', 'Noto Sans SC', system-ui, sans-serif;
}
.result-rule {
  font-size: 13px; color: var(--text-muted); margin-top: 8px;
}
.result-copy {
  margin-top: 12px;
  padding: 8px 20px;
  background: var(--surface); border: 1px solid var(--border);
  border-radius: 100px;
  font-family: inherit; font-size: 13px; font-weight: 500;
  color: var(--text-secondary); cursor: pointer;
  transition: all 0.15s ease;
}
.result-copy:hover { border-color: var(--primary); color: var(--primary); background: var(--primary-light); }

.direction-tabs {
  display: flex; gap: 4px; margin-bottom: 20px;
  padding: 4px; background: var(--bg-alt);
  border: 1px solid var(--border); border-radius: 100px;
}
.dir-tab {
  flex: 1; padding: 10px 20px; background: none; border: none;
  border-radius: 100px;
  font-family: inherit; font-size: 14px; font-weight: 500;
  color: var(--text-muted); cursor: pointer;
  transition: all 0.2s ease;
}
.dir-tab.active { background: var(--surface); color: var(--text); font-weight: 600; box-shadow: 0 1px 3px rgba(0,0,0,0.08); }

.irregular-table {
  width: 100%; border-collapse: separate; border-spacing: 0;
  border: 1px solid var(--border); border-radius: var(--radius); overflow: hidden;
}
.irregular-table th {
  padding: 12px 16px; background: var(--bg-alt);
  font-size: 12px; font-weight: 600; text-transform: uppercase;
  letter-spacing: 0.05em; color: var(--text-muted);
  text-align: left; border-bottom: 1px solid var(--border);
}
.irregular-table td {
  padding: 10px 16px; font-size: 14px; color: var(--text);
  border-bottom: 1px solid var(--border);
}
.irregular-table tr:last-child td { border-bottom: none; }
.irregular-table tr:hover td { background: var(--primary-light); }

.guide-section {
  margin-top: 16px; margin-bottom: 64px;
  background: #ffffff; border: 1px solid var(--border);
  border-radius: 12px; overflow: hidden;
}
.guide-toggle {
  display: flex; align-items: center; justify-content: space-between;
  width: 100%; padding: 14px 20px;
  background: none; border: none; cursor: pointer;
  transition: background 0.15s ease;
}
.guide-toggle:hover { background: var(--bg-alt); }
.guide-toggle-title { display: flex; align-items: center; gap: 8px; font-size: 14px; font-weight: 600; color: #1E293B; }
.guide-toggle.open .toggle-arrow { transform: rotate(180deg); }
.toggle-arrow { transition: transform 0.2s ease; color: var(--text-muted); }
.guide-list { padding: 0 20px 20px; }
.guide-list.hidden { display: none; }
.guide-item { padding: 16px 0; border-top: 1px solid var(--border); }
.guide-item:first-child { border-top: 1px solid var(--border); }
.guide-item-title { font-size: 14px; font-weight: 600; color: #1E293B; margin-bottom: 6px; }
.guide-item-body { font-size: 13px; color: var(--text-secondary); line-height: 1.8; }
.guide-item-body kbd { padding: 1px 6px; background: var(--bg-alt); border: 1px solid var(--border-strong); border-radius: 4px; font-family: 'SF Mono', 'Cascadia Code', monospace; font-size: 12px; color: var(--text-secondary); }

::-webkit-scrollbar { width: 8px; }
::-webkit-scrollbar-track { background: #f1f5f9; }
::-webkit-scrollbar-thumb { background: #A5B4FC; border-radius: 4px; }
::-webkit-scrollbar-thumb:hover { background: var(--primary); }
::selection { background: rgba(79, 70, 229, 0.2); color: #1E293B; }

@media (max-width: 768px) {
  .page { padding: 0 16px; }
  .input-row { flex-direction: column; }
  .btn-group { width: 100%; }
  .btn-primary, .btn-secondary { flex: 1; text-align: center; }
  .irregular-table { font-size: 12px; }
  .irregular-table th, .irregular-table td { padding: 8px 10px; }
}