:root {
    --bg-canvas: #0d1117;
    --bg-box: #161b22;
    --border-default: #30363d;
    --fg-default: #e6edf3;
    --fg-muted: #7d8590;
    --accent: #2f81f7;
    --header-bg: #010409;
    --card-hover: rgba(255,255,255,0.03);
    --sidebar-width: 260px;
    --header-height: 60px;
}

[data-theme="light"] {
    --bg-canvas: #ffffff;
    --bg-box: #ffffff;
    --border-default: #d0d7de;
    --fg-default: #1f2328;
    --fg-muted: #65717e;
    --accent: #0969da;
    --header-bg: #f6f8fa;
    --card-hover: #f6f8fa;
}

* { box-sizing: border-box; transition: background 0.2s, border-color 0.2s; }

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif;
    background-color: var(--bg-canvas);
    color: var(--fg-default);
    margin: 0;
    line-height: 1.5;
}

/* --- Header --- */
header {
    background-color: var(--header-bg);
    border-bottom: 1px solid var(--border-default);
    padding: 0 32px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    height: var(--header-height);
    z-index: 1000;
}

.brand { font-size: 16px; font-weight: 600; color: var(--fg-default); text-decoration: none; }
.header-actions { display: flex; gap: 8px; }

.icon-btn {
    background: transparent; border: 1px solid var(--border-default);
    color: var(--fg-default); width: 32px; height: 32px;
    border-radius: 6px; cursor: pointer; display: flex; align-items: center; justify-content: center;
}
.icon-btn:hover { background-color: var(--border-default); }
.icon-btn svg { width: 18px; height: 18px; }

/* --- Sidebar --- */
.sidebar {
    position: fixed;
    top: var(--header-height);
    left: 0;
    bottom: 0;
    width: var(--sidebar-width);
    background-color: var(--bg-canvas);
    border-right: 1px solid var(--border-default);
    padding: 32px 24px;
    overflow-y: auto;
    z-index: 900;
}

.sidebar nav { display: flex; flex-direction: column; gap: 4px; }
.side-item {
    padding: 8px 12px; border-radius: 6px; cursor: pointer;
    font-size: 14px; color: var(--fg-default); text-decoration: none;
    display: block;
}
.side-item:hover { background-color: var(--card-hover); }
.side-item.active { background-color: rgba(47, 129, 247, 0.1); color: var(--accent); font-weight: 600; }

/* --- Main Content --- */
.container {
    margin-top: var(--header-height);
    padding-left: var(--sidebar-width);
    display: flex;
    justify-content: center;
}

main {
    width: 100%;
    max-width: 1100px;
    padding: 40px 32px;
}

.section-label { font-size: 11px; font-weight: 600; margin-bottom: 12px; color: var(--fg-muted); text-transform: uppercase; letter-spacing: 0.5px; }

.category-title {
    margin: 32px 0 16px 0;
    color: var(--fg-default);
    border-left: 4px solid var(--accent);
    padding-left: 12px;
    font-size: 18px;
}

.resource-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 20px;
}

/* --- Card Style --- */
.card {
    background-color: var(--bg-box); border: 1px solid var(--border-default);
    border-radius: 12px; padding: 24px; display: flex; flex-direction: column;
    text-decoration: none; color: inherit; height: 100%;
    transition: transform 0.2s, border-color 0.2s;
}
.card:hover { border-color: var(--accent); transform: translateY(-2px); }
.card-title { font-size: 16px; font-weight: 600; color: var(--accent); margin-bottom: 8px; }
.card-desc { font-size: 13px; color: var(--fg-muted); margin-bottom: 20px; flex-grow: 1; }
.badge { font-size: 10px; padding: 2px 8px; border: 1px solid var(--border-default); border-radius: 12px; color: var(--fg-muted); }

#toast {
    position: fixed; bottom: 24px; right: 24px;
    background: var(--fg-default); color: var(--bg-canvas);
    padding: 10px 20px; border-radius: 8px; font-size: 13px;
    opacity: 0; transition: 0.3s; z-index: 2000;
    pointer-events: none;
}

@media (max-width: 1024px) {
    .sidebar { transform: translateX(-100%); transition: transform 0.3s; }
    .container { padding-left: 0; }
}