:root {
    --primary-color: #2d5f7f;
    --primary-dark: #1e4159;
    --secondary-color: #5cb85c;
    --danger-color: #dc3545;
    --bg-color: #f4f6f9;
    --card-bg: #ffffff;
    --text-primary: #2c3e50;
    --text-secondary: #6c757d;
    --border-color: #dee2e6;
    --shadow-sm: 0 2px 4px rgba(0,0,0,0.1);
    --shadow-md: 0 4px 6px rgba(0,0,0,0.1);
    --radius-sm: 6px;
    --radius-md: 10px;
    --sidebar-width: 260px;
    --header-height: 70px;
}

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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: var(--bg-color);
    color: var(--text-primary);
}

/* Header - Fixed */
.main-header {
    background: linear-gradient(135deg, #2d5f7f 0%, #1e4159 100%);
    color: white;
    padding: 0 2rem;
    box-shadow: var(--shadow-md);
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    height: var(--header-height);
    z-index: 1000;
    display: flex;
    align-items: center;
}

.header-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
    width: 100%;
}

.header-left {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.menu-toggle {
    font-size: 1.5rem;
    cursor: pointer;
    padding: 0.5rem;
    border: none;
    background: none;
    color: white;
}

.header-logo {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

    .header-logo h1 {
        font-size: 1.3rem;
        font-weight: 600;
    }

.header-actions {
    display: flex;
    gap: 1rem;
    align-items: center;
}

.header-select {
    background: rgba(255, 255, 255, 0.15);
    border: 1px solid rgba(255, 255, 255, 0.3);
    color: white;
    padding: 0.6rem 1rem;
    border-radius: var(--radius-sm);
    font-size: 0.9rem;
    min-width: 150px;
}

.header-btn {
    padding: 0.6rem 1.2rem;
    border: none;
    border-radius: var(--radius-sm);
    cursor: pointer;
    font-weight: 500;
    font-size: 0.9rem;
    transition: all 0.3s;
}

    .header-btn.success {
        background: var(--secondary-color);
        color: white;
    }

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

    .header-btn:hover {
        opacity: 0.9;
    }

/* Sidebar - Fixed */
.sidebar {
    position: fixed;
    left: 0;
    top: var(--header-height);
    width: var(--sidebar-width);
    height: calc(100vh - var(--header-height));
    background: white;
    box-shadow: 2px 0 5px rgba(0,0,0,0.1);
    overflow-y: auto;
    z-index: 999;
}

.sidebar-menu {
    list-style: none;
    padding: 0;
}

.sidebar-item {
    margin: 0;
}

.sidebar-link {
    display: flex;
    align-items: center;
    gap: 1rem;
    padding: 1rem 1.5rem;
    color: var(--text-secondary);
    text-decoration: none;
    transition: all 0.3s;
    border-left: 3px solid transparent;
}

    .sidebar-link:hover {
        background: #f0f4f8;
        color: var(--primary-color);
    }

    .sidebar-link.active {
        background: #e8f4f8;
        color: var(--primary-color);
        border-left-color: var(--primary-color);
        font-weight: 600;
    }

.sidebar-icon {
    font-size: 1.2rem;
    width: 24px;
}

/* Main Content - Properly positioned */
.main-wrapper {
    margin-left: var(--sidebar-width);
    margin-top: var(--header-height);
    min-height: calc(100vh - var(--header-height));
    padding: 2rem;
}