/* ===================================================================
   1. CSS Variables - Color Palette (预留选项，计划文档采用直写颜色值)
   =================================================================== */

/* ===================================================================
   2. CSS Reset & Base
   =================================================================== */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  border-width: 0;
  border-style: solid;
  border-color: #e5e7eb;   /* 使用与 Tailwind 默认相近的中性色，方便后续 border 类覆盖 */
}
body {
  font-family: ui-sans-serif, system-ui, -apple-system, sans-serif;
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}
button,
input,
optgroup,
select,
textarea {
  font-family: inherit;
  font-size: 100%;
  font-weight: inherit;
  line-height: inherit;
  color: inherit;
  margin: 0;
  padding: 0;
}

button,
[type='button'],
[type='reset'],
[type='submit'] {
  -webkit-appearance: button;
  background-color: transparent;
  background-image: none;
}
/* ===================================================================
   3. Layout & Display
   =================================================================== */
.block        { display: block; }
.inline-block { display: inline-block; }
.inline-flex  { display: inline-flex; }
.flex         { display: flex; }
.grid         { display: grid; }
.relative     { position: relative; }

/* ===================================================================
   4. Flexbox & Grid
   =================================================================== */
.flex-col       { flex-direction: column; }
.flex-wrap      { flex-wrap: wrap; }
.items-center   { align-items: center; }
.items-start    { align-items: flex-start; }
.justify-center { justify-content: center; }
.justify-between { justify-content: space-between; }
.justify-start  { justify-content: flex-start; }
.auto-rows-fr   { grid-auto-rows: minmax(0, 1fr); }
.grid-cols-1    { grid-template-columns: repeat(1, minmax(0, 1fr)); }
.grid-cols-2    { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.grid-cols-3    { grid-template-columns: repeat(3, minmax(0, 1fr)); }
/* 添加到第 4 节的适当位置 */
.gap-1   { gap: 0.25rem; }
.gap-1\.5 { gap: 0.375rem; }
.gap-2   { gap: 0.5rem; }
.gap-3   { gap: 0.75rem; }
.gap-4   { gap: 1rem; }
.gap-5   { gap: 1.25rem; }
.gap-6   { gap: 1.5rem; }
.gap-7   { gap: 1.75rem; }
/* lg: grid 列跨度会放入响应式章节 */
.lg\:grid-cols-12 { grid-template-columns: repeat(12, minmax(0, 1fr)); }
.lg\:col-span-4   { grid-column: span 4 / span 4; }
.lg\:col-span-8   { grid-column: span 8 / span 8; }
.lg\:col-span-3   { grid-column: span 3 / span 3; }
.lg\:col-span-9   { grid-column: span 9 / span 9; }

/* ===================================================================
   5. Sizing - Width & Height
   =================================================================== */
.w-1   { width: 0.25rem; }
.w-3   { width: 0.75rem; }
.w-4   { width: 1rem; }
.w-5   { width: 1.25rem; }
.w-8   { width: 2rem; }
.w-10  { width: 2.5rem; }
.w-full { width: 100%; }
.h-0\.5 { height: 0.125rem; }
.h-1   { height: 0.25rem; }
.h-3   { height: 0.75rem; }
.h-4   { height: 1rem; }
.h-5   { height: 1.25rem; }
.h-6   { height: 1.5rem; }
.h-8   { height: 2rem; }
.h-10  { height: 2.5rem; }
.max-w-2xl { max-width: 42rem; }
.max-w-7xl { max-width: 80rem; }

/* ===================================================================
   6. Spacing - Padding
   =================================================================== */
.p-2  { padding: 0.5rem; }
.p-3  { padding: 0.75rem; }
.p-4  { padding: 1rem; }
.p-5  { padding: 1.25rem; }
.p-6  { padding: 1.5rem; }
.px-2 { padding-left: 0.5rem; padding-right: 0.5rem; }
.px-3 { padding-left: 0.75rem; padding-right: 0.75rem; }
.px-4 { padding-left: 1rem; padding-right: 1rem; }
.px-5 { padding-left: 1.25rem; padding-right: 1.25rem; }
.px-6 { padding-left: 1.5rem; padding-right: 1.5rem; }
.py-0\.5 { padding-top: 0.125rem; padding-bottom: 0.125rem; }
.py-1 { padding-top: 0.25rem; padding-bottom: 0.25rem; }
.py-2 { padding-top: 0.5rem; padding-bottom: 0.5rem; }
.py-6 { padding-top: 1.5rem; padding-bottom: 1.5rem; }
.pb-2 { padding-bottom: 0.5rem; }
.pb-4 { padding-bottom: 1rem; }
.pb-6 { padding-bottom: 1.5rem; }
.pl-4 { padding-left: 1rem; }
.pt-2 { padding-top: 0.5rem; }
.pt-6 { padding-top: 1.5rem; }

/* ===================================================================
   7. Spacing - Margin
   =================================================================== */
.m-1  { margin: 0.25rem; }
.ml-1 { margin-left: 0.25rem; }
.ml-2 { margin-left: 0.5rem; }
.mr-1 { margin-right: 0.25rem; }
.mx-auto { margin-left: auto; margin-right: auto; }
.my-3 { margin-top: 0.75rem; margin-bottom: 0.75rem; }
.mt-1  { margin-top: 0.25rem; }
.mt-2  { margin-top: 0.5rem; }
.mt-3  { margin-top: 0.75rem; }
.mt-4  { margin-top: 1rem; }
.mt-6  { margin-top: 1.5rem; }
.mt-8  { margin-top: 2rem; }
.mt-12 { margin-top: 3rem; }
.mb-1  { margin-bottom: 0.25rem; }
.mb-2  { margin-bottom: 0.5rem; }
.mb-3  { margin-bottom: 0.75rem; }
.mb-4  { margin-bottom: 1rem; }
.mb-5  { margin-bottom: 1.25rem; }
.mb-8  { margin-bottom: 2rem; }
.mb-10 { margin-bottom: 2.5rem; }
.mb-12 { margin-bottom: 3rem; }
/* Space Between - 垂直间距 (类似 gap 但用于普通流式布局) */
.space-y-1 > * + * { margin-top: 0.25rem; }
.space-y-2 > * + * { margin-top: 0.5rem; }
.space-y-3 > * + * { margin-top: 0.75rem; }
.space-y-4 > * + * { margin-top: 1rem; }
.space-y-5 > * + * { margin-top: 1.25rem; }
.space-y-6 > * + * { margin-top: 1.5rem; }

/* ===================================================================
   8. Typography - Size & Weight
   =================================================================== */
.font-sans     { font-family: ui-sans-serif, system-ui, -apple-system, sans-serif; }
.font-mono     { font-family: ui-monospace, SFMono-Regular, Menlo, monospace; }
.font-medium   { font-weight: 500; }
.font-semibold { font-weight: 600; }
.font-bold     { font-weight: 700; }
.font-extrabold { font-weight: 800; }

.text-xs   { font-size: 0.75rem; line-height: 1rem; }
.text-sm   { font-size: 0.875rem; line-height: 1.25rem; }
.text-base { font-size: 1rem; line-height: 1.5rem; }
.text-md   { font-size: 1rem; line-height: 1.5rem; }
.text-lg   { font-size: 1.125rem; line-height: 1.75rem; }
.text-xl   { font-size: 1.25rem; line-height: 1.75rem; }
.text-2xl  { font-size: 1.5rem; line-height: 2rem; }
.text-3xl  { font-size: 1.875rem; line-height: 2.25rem; }
.text-4xl  { font-size: 2.25rem; line-height: 2.5rem; }
.text-5xl  { font-size: 3rem; line-height: 1; }
.text-\[10px\] { font-size: 10px; }
.text-\[11px\] { font-size: 11px; }

.text-center { text-align: center; }
.leading-relaxed { line-height: 1.625; }
.tracking-tight { letter-spacing: -0.025em; }
.list-disc { list-style-type: disc; }
.antialiased { -webkit-font-smoothing: antialiased; -moz-osx-font-smoothing: grayscale; }

/* ===================================================================
   9. Text Colors
   =================================================================== */
.text-transparent { color: transparent; }
.text-white       { color: #fff; }

.text-slate-300 { color: #cbd5e1; }
.text-slate-400 { color: #94a3b8; }
.text-slate-500 { color: #64748b; }
.text-slate-600 { color: #475569; }
.text-slate-700 { color: #334155; }
.text-slate-800 { color: #1e293b; }

.text-blue-400 { color: #60a5fa; }
.text-blue-500 { color: #3b82f6; }
.text-blue-600 { color: #2563eb; }
.text-blue-700 { color: #1d4ed8; }

.text-indigo-500 { color: #6366f1; }
.text-indigo-600 { color: #4f46e5; }
.text-indigo-700 { color: #4338ca; }
.text-indigo-800 { color: #3730a3; }

.text-red-400 { color: #f87171; }
.text-red-500 { color: #ef4444; }
.text-red-600 { color: #dc2626; }
.text-red-700 { color: #b91c1c; }

.text-green-400 { color: #4ade80; }
.text-green-500 { color: #22c55e; }
.text-green-600 { color: #16a34a; }
.text-green-700 { color: #15803d; }

.text-purple-400 { color: #c084fc; }
.text-purple-500 { color: #a855f7; }
.text-purple-600 { color: #9333ea; }
.text-purple-700 { color: #7e22ce; }

.text-amber-500 { color: #f59e0b; }
.text-amber-600 { color: #d97706; }
.text-amber-700 { color: #b45309; }

.text-orange-500 { color: #f97316; }
.text-orange-600 { color: #ea580c; }
.text-orange-700 { color: #c2410c; }

.text-emerald-500 { color: #10b981; }
.text-emerald-600 { color: #059669; }
.text-emerald-700 { color: #047857; }

.text-rose-500 { color: #f43f5e; }
.text-rose-600 { color: #e11d48; }
.text-rose-700 { color: #be123c; }

.text-pink-500 { color: #ec4899; }
.text-pink-600 { color: #db2777; }
.text-pink-700 { color: #be185d; }

.text-cyan-500 { color: #06b6d4; }
.text-cyan-600 { color: #0891b2; }
.text-cyan-700 { color: #0e7490; }

.text-sky-500 { color: #0ea5e9; }
.text-sky-600 { color: #0284c7; }
.text-sky-700 { color: #0369a1; }

.text-teal-500 { color: #14b8a6; }
.text-teal-600 { color: #0d9488; }
.text-teal-700 { color: #0f766e; }

.text-violet-500 { color: #8b5cf6; }
.text-violet-600 { color: #7c3aed; }
.text-violet-700 { color: #6d28d9; }

.text-fuchsia-500 { color: #d946ef; }
.text-fuchsia-600 { color: #c026d3; }
.text-fuchsia-700 { color: #a21caf; }

.text-lime-500 { color: #84cc16; }
.text-lime-600 { color: #65a30d; }
.text-lime-700 { color: #4d7c0f; }

.text-yellow-500 { color: #eab308; }
.text-yellow-600 { color: #ca8a04; }

/* 100 级浅色文字 */
.text-blue-100 { color: #dbeafe; }
.text-indigo-100 { color: #e0e7ff; }
.text-red-100 { color: #fee2e2; }
.text-green-100 { color: #dcfce7; }
.text-purple-100 { color: #f3e8ff; }
.text-amber-100 { color: #fef3c7; }
.text-orange-100 { color: #ffedd5; }
.text-emerald-100 { color: #d1fae5; }
.text-rose-100 { color: #ffe4e6; }
.text-pink-100 { color: #fce7f3; }
.text-cyan-100 { color: #cffafe; }
.text-sky-100 { color: #e0f2fe; }
.text-teal-100 { color: #ccfbf1; }
.text-violet-100 { color: #ede9fe; }
.text-fuchsia-100 { color: #fae8ff; }
.text-lime-100 { color: #ecfccb; }
.text-yellow-100 { color: #fef9c3; }

/* ===================================================================
   10. Background Colors
   =================================================================== */
.bg-white { background-color: #fff; }
.bg-white\/60 { background-color: rgba(255,255,255,0.6); }
.bg-white\/70 { background-color: rgba(255,255,255,0.7); }
.bg-white\/80 { background-color: rgba(255,255,255,0.8); }
.bg-white\/90 { background-color: rgba(255,255,255,0.9); }

.bg-slate-50  { background-color: #f8fafc; }
.bg-slate-100 { background-color: #f1f5f9; }

.bg-blue-50   { background-color: #eff6ff; }
.bg-blue-100  { background-color: #dbeafe; }
.bg-blue-400  { background-color: #60a5fa; }
.bg-blue-500  { background-color: #3b82f6; }

.bg-indigo-50  { background-color: #eef2ff; }
.bg-indigo-100 { background-color: #e0e7ff; }
.bg-indigo-500 { background-color: #6366f1; }

.bg-red-50   { background-color: #fef2f2; }
.bg-red-400  { background-color: #f87171; }
.bg-red-500  { background-color: #ef4444; }

.bg-green-50  { background-color: #f0fdf4; }
.bg-green-100 { background-color: #dcfce7; }
.bg-green-400 { background-color: #4ade80; }
.bg-green-500 { background-color: #22c55e; }

.bg-purple-50  { background-color: #faf5ff; }
.bg-purple-100 { background-color: #f3e8ff; }
.bg-purple-400 { background-color: #c084fc; }
.bg-purple-500 { background-color: #a855f7; }

.bg-amber-50  { background-color: #fffbeb; }
.bg-amber-100 { background-color: #fef3c7; }
.bg-amber-500 { background-color: #f59e0b; }

.bg-orange-50  { background-color: #fff7ed; }
.bg-orange-100 { background-color: #ffedd5; }
.bg-orange-400 { background-color: #fb923c; }
.bg-orange-500 { background-color: #f97316; }

.bg-emerald-50  { background-color: #ecfdf5; }
.bg-emerald-100 { background-color: #d1fae5; }
.bg-emerald-500 { background-color: #10b981; }

.bg-rose-100 { background-color: #ffe4e6; }
.bg-pink-100 { background-color: #fce7f3; }
.bg-cyan-100 { background-color: #cffafe; }
.bg-cyan-500 { background-color: #06b6d4; }
.bg-sky-100 { background-color: #e0f2fe; }
.bg-teal-100 { background-color: #ccfbf1; }
.bg-violet-100 { background-color: #ede9fe; }
.bg-fuchsia-100 { background-color: #fae8ff; }
.bg-lime-100 { background-color: #ecfccb; }
.bg-lime-500 { background-color: #84cc16; }
.bg-yellow-100 { background-color: #fef9c3; }

/* ===================================================================
   11. Gradients
   =================================================================== */
.bg-gradient-to-br {
  background-image: linear-gradient(to bottom right, var(--tw-gradient-stops));
}
.bg-gradient-to-r {
  background-image: linear-gradient(to right, var(--tw-gradient-stops));
}
.from-slate-50 {
  --tw-gradient-from: #f8fafc;
  --tw-gradient-to: transparent;
  --tw-gradient-stops: var(--tw-gradient-from), var(--tw-gradient-to);
}
.from-indigo-600 {
  --tw-gradient-from: #4f46e5;
  --tw-gradient-to: transparent;
  --tw-gradient-stops: var(--tw-gradient-from), var(--tw-gradient-to);
}
.from-amber-50\/30 {
  --tw-gradient-from: rgba(255,251,235,0.3);
  --tw-gradient-to: transparent;
  --tw-gradient-stops: var(--tw-gradient-from), var(--tw-gradient-to);
}
.from-amber-500 {
  --tw-gradient-from: #f59e0b;
  --tw-gradient-to: transparent;
  --tw-gradient-stops: var(--tw-gradient-from), var(--tw-gradient-to);
}
.via-blue-600 {
  --tw-gradient-to: transparent;
  --tw-gradient-stops: var(--tw-gradient-from), #2563eb, var(--tw-gradient-to);
}
.to-slate-100 {
  --tw-gradient-to: #f1f5f9;
}
.to-blue-600 {
  --tw-gradient-to: #2563eb;
}
.to-cyan-600 {
  --tw-gradient-to: #0891b2;
}
.to-orange-50\/40 {
  --tw-gradient-to: rgba(255,247,237,0.4);
}
.to-orange-600 {
  --tw-gradient-to: #ea580c;
}
.bg-clip-text {
  -webkit-background-clip: text;
  background-clip: text;
}

/* ===================================================================
   12. Borders & Border Radius
   =================================================================== */
.border      { border-width: 1px; }
.border-t    { border-top-width: 1px; }
.border-l-2  { border-left-width: 2px; }
.border-l-4  { border-left-width: 4px; }

.border-slate-100 { border-color: #f1f5f9; }
.border-slate-200 { border-color: #e2e8f0; }
.border-slate-200\/60 { border-color: rgba(226,232,240,0.6); }
.border-slate-200\/80 { border-color: rgba(226,232,240,0.8); }
.border-red-100     { border-color: #fee2e2; }
.border-green-100   { border-color: #dcfce7; }
.border-blue-100    { border-color: #dbeafe; }
.border-emerald-300 { border-color: #6ee7b7; }
.border-emerald-400 { border-color: #34d399; }

.rounded     { border-radius: 0.25rem; }
.rounded-md  { border-radius: 0.375rem; }
.rounded-lg  { border-radius: 0.5rem; }
.rounded-xl  { border-radius: 0.75rem; }
.rounded-2xl { border-radius: 1rem; }
.rounded-full { border-radius: 9999px; }

/* ===================================================================
   13. Shadows
   =================================================================== */
.shadow-sm {
  box-shadow: 0 1px 2px 0 rgba(0,0,0,0.05);
}
.shadow-md {
  box-shadow: 0 4px 6px -1px rgba(0,0,0,0.1), 0 2px 4px -2px rgba(0,0,0,0.1);
}
.shadow-lg {
  box-shadow: 0 10px 15px -3px rgba(0,0,0,0.1), 0 4px 6px -4px rgba(0,0,0,0.1);
}
.shadow-xl {
  box-shadow: 0 20px 25px -5px rgba(0,0,0,0.1), 0 8px 10px -6px rgba(0,0,0,0.1);
}

/* ===================================================================
   14. Effects & Transitions
   =================================================================== */
.backdrop-blur-sm {
  backdrop-filter: blur(4px);
  -webkit-backdrop-filter: blur(4px);
}
.transition {
  transition-property: color, background-color, border-color, fill, stroke, opacity, box-shadow, transform, filter, backdrop-filter;
  transition-timing-function: cubic-bezier(0.4, 0, 0.2, 1);
  transition-duration: 150ms;
}
.transition-all {
  transition-property: all;
  transition-timing-function: cubic-bezier(0.4, 0, 0.2, 1);
  transition-duration: 150ms;
}
.transition-colors {
  transition-property: color, background-color, border-color, fill, stroke;
  transition-timing-function: cubic-bezier(0.4, 0, 0.2, 1);
  transition-duration: 150ms;
}
.duration-200 {
  transition-duration: 200ms;
}

/* ===================================================================
   15. Interactive States - Hover & Focus
   =================================================================== */
/* Hover background */
.hover\:bg-blue-100:hover { background-color: #dbeafe; }
.hover\:bg-blue-600:hover { background-color: #2563eb; }
.hover\:bg-amber-100:hover { background-color: #fef3c7; }

/* Hover shadow */
.hover\:shadow-xl:hover {
  box-shadow: 0 20px 25px -5px rgba(0,0,0,0.1), 0 8px 10px -6px rgba(0,0,0,0.1);
}

/* Hover text colors */
.hover\:text-blue-500:hover { color: #3b82f6; }
.hover\:text-blue-700:hover { color: #1d4ed8; }
.hover\:text-blue-800:hover { color: #1e40af; }
.hover\:text-amber-700:hover { color: #b45309; }
.hover\:text-amber-900:hover { color: #78350f; }
.hover\:text-indigo-500:hover { color: #6366f1; }
.hover\:text-indigo-700:hover { color: #4338ca; }
.hover\:text-rose-500:hover { color: #f43f5e; }
.hover\:text-rose-700:hover { color: #be123c; }
.hover\:text-emerald-500:hover { color: #10b981; }
.hover\:text-emerald-700:hover { color: #047857; }
.hover\:text-orange-500:hover { color: #f97316; }
.hover\:text-orange-700:hover { color: #c2410c; }
.hover\:text-cyan-500:hover { color: #06b6d4; }
.hover\:text-cyan-700:hover { color: #0e7490; }
.hover\:text-sky-500:hover { color: #0ea5e9; }
.hover\:text-sky-700:hover { color: #0369a1; }
.hover\:text-violet-500:hover { color: #8b5cf6; }
.hover\:text-violet-700:hover { color: #6d28d9; }
.hover\:text-fuchsia-500:hover { color: #d946ef; }
.hover\:text-fuchsia-700:hover { color: #a21caf; }
.hover\:text-pink-500:hover { color: #ec4899; }
.hover\:text-pink-700:hover { color: #be185d; }
.hover\:text-purple-500:hover { color: #a855f7; }
.hover\:text-purple-700:hover { color: #7e22ce; }
.hover\:text-green-500:hover { color: #22c55e; }
.hover\:text-green-700:hover { color: #15803d; }
.hover\:text-lime-500:hover { color: #84cc16; }
.hover\:text-lime-700:hover { color: #4d7c0f; }
.hover\:text-teal-500:hover { color: #14b8a6; }
.hover\:text-teal-700:hover { color: #0f766e; }
.hover\:text-yellow-500:hover { color: #eab308; }
.hover\:text-yellow-700:hover { color: #a16207; }

/* Focus */
.focus\:outline-none:focus { outline: 2px solid transparent; outline-offset: 2px; }
.focus\:ring-2:focus { box-shadow: 0 0 0 3px rgba(59,130,246,0.5); }
.focus\:ring-blue-300:focus { box-shadow: 0 0 0 3px rgba(147,197,253,0.5); }
.focus\:ring-green-300:focus { box-shadow: 0 0 0 3px rgba(134,239,172,0.5); }
.focus\:ring-emerald-300:focus { box-shadow: 0 0 0 3px rgba(110,231,183,0.5); }

/* ===================================================================
   16. Responsive Breakpoints
   =================================================================== */
@media (min-width: 640px) {
  .sm\:grid-cols-2 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .sm\:flex-row { flex-direction: row; }
}

@media (min-width: 768px) {
  .md\:grid-cols-2 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .md\:grid-cols-3 { grid-template-columns: repeat(3, minmax(0, 1fr)); }
  .md\:gap-7 { gap: 1.75rem; }
  .md\:py-8 { padding-top: 2rem; padding-bottom: 2rem; }
  .md\:py-10 { padding-top: 2.5rem; padding-bottom: 2.5rem; }
  .md\:text-lg { font-size: 1.125rem; line-height: 1.75rem; }
  .md\:text-3xl { font-size: 1.875rem; line-height: 2.25rem; }
  .md\:text-4xl { font-size: 2.25rem; line-height: 2.5rem; }
  .md\:text-5xl { font-size: 3rem; line-height: 1; }
}

@media (min-width: 1024px) {
  .lg\:grid-cols-2  { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .lg\:grid-cols-3  { grid-template-columns: repeat(3, minmax(0, 1fr)); }
  .lg\:grid-cols-12 { grid-template-columns: repeat(12, minmax(0, 1fr)); }
  .lg\:col-span-3   { grid-column: span 3 / span 3; }
  .lg\:col-span-4   { grid-column: span 4 / span 4; }
  .lg\:col-span-8   { grid-column: span 8 / span 8; }
  .lg\:col-span-9   { grid-column: span 9 / span 9; }
}

/* ===================================================================
   17. Custom Component Classes
   =================================================================== */
/* 卡片悬停动画 */
.card-hover {
  transition: transform 0.2s ease, box-shadow 0.2s ease;
}
.card-hover:hover {
  transform: translateY(-4px);
  box-shadow: 0 12px 24px rgba(0, 0, 0, 0.1);
}

/* 导航卡片（index.html） */
.nav-card:active {
  transform: scale(0.98);
}
.nav-card:focus-visible {
  outline: 2px solid #3b82f6;
  outline-offset: 2px;
}

/* 章节标题渐变下划线（index.html） */
.section-title {
  position: relative;
  display: inline-block;
}
.section-title::after {
  content: '';
  position: absolute;
  bottom: -4px;
  left: 0;
  width: 100%;
  height: 3px;
  background: linear-gradient(to right, #4f46e5, #2563eb);
  border-radius: 2px;
}

/* 波形卡片过渡 */
.wave-card {
  transition: opacity 0.3s ease, transform 0.3s ease;
}

/* 双列布局（Fourier 文件） */
.two-columns {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 1rem;
}
@media (max-width: 768px) {
  .two-columns {
    grid-template-columns: 1fr;
  }
}

/* 重置按钮悬停 */
.reset-btn {
  transition: transform 0.15s ease, box-shadow 0.15s ease;
}
.reset-btn:hover {
  transform: translateY(-1px);
  box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
}

/* 全局滚动条样式（index.html） */
::-webkit-scrollbar {
  width: 8px;
}
::-webkit-scrollbar-track {
  background: #f1f5f9;
}
::-webkit-scrollbar-thumb {
  background: #94a3b8;
  border-radius: 4px;
}
::-webkit-scrollbar-thumb:hover {
  background: #64748b;
}