:root {
    /* Color Palette */
    --primary: #2563eb;
    --primary-hover: #1d4ed8;
    --secondary: #64748b;
    --success: #10b981;
    --danger: #ef4444;
    --warning: #f59e0b;
    --info: #0ea5e9;
    
    /* Backgrounds */
    --bg-main: #f8fafc;
    --bg-surface: #ffffff;
    --bg-sidebar: #1e293b;
    
    /* Text */
    --text-main: #1e293b;
    --text-muted: #64748b;
    --text-on-dark: #f8fafc;
    
    /* Borders & Shadows */
    --border-color: #e2e8f0;
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
    
    /* Transitions */
    --transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Inter', system-ui, -apple-system, sans-serif;
    background-color: var(--bg-main);
    color: var(--text-main);
    line-height: 1.5;
    -webkit-font-smoothing: antialiased;
}

/* Layout */
.app-container {
    display: grid;
    grid-template-columns: 260px 1fr;
    min-height: 100vh;
}

/* Sidebar */
.sidebar {
    background-color: var(--bg-sidebar);
    color: var(--text-on-dark);
    padding: 1.5rem;
    display: flex;
    flex-direction: column;
    gap: 2rem;
}

.sidebar-brand {
    font-size: 1.25rem;
    font-weight: 700;
    color: #fff;
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

.sidebar-nav {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.nav-link {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    padding: 0.75rem 1rem;
    border-radius: 0.5rem;
    color: #94a3b8;
    text-decoration: none;
    transition: var(--transition);
}

.nav-link:hover, .nav-link.active {
    background-color: rgba(255, 255, 255, 0.1);
    color: #fff;
}

/* Header */
.main-content {
    display: flex;
    flex-direction: column;
}

header {
    background-color: var(--bg-surface);
    height: 64px;
    padding: 0 2rem;
    display: flex;
    align-items: center;
    justify-content: space-between;
    border-bottom: 1px solid var(--border-color);
    box-shadow: var(--shadow-sm);
}

.user-profile {
    display: flex;
    align-items: center;
    gap: 1rem;
    cursor: pointer;
}

.avatar {
    width: 32px;
    height: 32px;
    background-color: var(--primary);
    color: white;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 600;
    font-size: 0.875rem;
}

/* Page Content */
.page-container {
    padding: 2rem;
    flex: 1;
}

.card {
    background-color: var(--bg-surface);
    border-radius: 0.75rem;
    border: 1px solid var(--border-color);
    box-shadow: var(--shadow-sm);
    padding: 1.5rem;
    margin-bottom: 1.5rem;
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 0.5rem 1rem;
    border-radius: 0.5rem;
    font-weight: 500;
    cursor: pointer;
    transition: var(--transition);
    border: 1px solid transparent;
    gap: 0.5rem;
}

.btn-primary {
    background-color: var(--primary);
    color: white;
}

.btn-primary:hover {
    background-color: var(--primary-hover);
}

.btn-outline {
    border-color: var(--border-color);
    background-color: transparent;
    color: var(--text-main);
}

.btn-outline:hover {
    background-color: var(--bg-main);
}

/* Typography */
h1 { font-size: 1.875rem; font-weight: 700; margin-bottom: 1rem; }
h2 { font-size: 1.5rem; font-weight: 600; margin-bottom: 0.75rem; }
.text-muted { color: var(--text-muted); font-size: 0.875rem; }