.bt-index { display: flex; flex-direction: column; gap: 26px; padding-bottom: 34px; min-width: 0; }
.bt-head h1 { font-size: 22px; font-weight: 600; color: var(--tw-gray-900); margin-bottom: 8px; }
.bt-head p { font-size: 13px; line-height: 1.6; margin: 0 0 4px; max-width: 860px; color: var(--tw-gray-700, #475569); }
.bt-index .bt-muted, .bt-card-meta, .bt-group-head p { color: var(--tw-gray-600, #64748b); }
.bt-group { display: flex; flex-direction: column; gap: 12px; min-width: 0; }
.bt-group-head { display: flex; flex-wrap: wrap; align-items: baseline; gap: 4px 12px; }
.bt-group-head h2 { display: flex; align-items: center; gap: 8px; font-size: 15px; font-weight: 600; color: var(--tw-gray-900); }
.bt-group-head h2 i { color: var(--tw-primary, #2563eb); font-size: 17px; }
.bt-group-head p { font-size: 12px; margin: 0; }
.bt-cards { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 12px; }
.bt-card { padding: 16px 18px; display: flex; flex-direction: column; gap: 8px; min-width: 0; text-decoration: none;
           border-color: var(--tw-gray-200, #e5e7eb); transition: border-color .15s, box-shadow .15s, transform .15s; }
.bt-card:hover { border-color: #6366f1; box-shadow: 0 2px 10px rgba(99, 102, 241, .13); transform: translateY(-1px); }
.bt-card-title { display: flex; align-items: center; justify-content: space-between; gap: 10px;
                 font-size: 14px; font-weight: 600; color: var(--tw-gray-900); }
.bt-card-title i { font-size: 13px; color: var(--tw-gray-400, #94a3b8); }
.bt-card:hover .bt-card-title, .bt-card:hover .bt-card-title i { color: #6366f1; }
.bt-card-note { font-size: 12px; line-height: 1.6; color: var(--tw-gray-700, #475569); }
.bt-card-meta { font-size: 11px; line-height: 1.5; font-variant-numeric: tabular-nums; }
.bt-foot { font-size: 12px; color: var(--tw-gray-600, #64748b); }
.bt-foot a { color: var(--tw-primary, #2563eb); }

@media (max-width: 900px) { .bt-cards { grid-template-columns: minmax(0, 1fr); } }

[data-theme-mode="dark"] .bt-card:hover { box-shadow: 0 2px 10px rgba(129, 140, 248, .18); border-color: #818cf8; }
[data-theme-mode="dark"] .bt-card:hover .bt-card-title,
[data-theme-mode="dark"] .bt-card:hover .bt-card-title i { color: #a5b4fc; }
[data-theme-mode="dark"] .bt-group-head h2 i { color: #818cf8; }