:root {
    --primary-gradient: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    --bg-color: #f8f9fa;
    --sidebar-bg: #ffffff;
    --card-hover: translateY(-5px);
}

body {
    background-color: var(--bg-color);
    font-family: 'Segoe UI', Roboto, "Helvetica Neue", Arial, sans-serif;
    overflow-x: hidden;
}

/* Sidebar Customization */
.sidebar-wrapper {
    height: 100vh;
    position: sticky;
    top: 0;
    border-right: 1px solid rgba(0,0,0,0.1);
    background: var(--sidebar-bg);
    overflow-y: auto;
}

.list-group-item {
    border: none;
    border-radius: 8px !important;
    margin-bottom: 5px;
    transition: all 0.2s ease;
}

.list-group-item.active {
    background: var(--primary-gradient);
    border: none;
    box-shadow: 0 4px 6px rgba(0,0,0,0.1);
}

.list-group-item:hover:not(.active) {
    background-color: #e9ecef;
    transform: translateX(5px);
}

/* Main Content Area */
.main-content {
    padding: 40px;
    min-height: 100vh;
}

/* Typography & Effects */
.text-gradient {
    background: var(--primary-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

/* Task Cards */
.task-card {
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.task-card:hover {
    transform: var(--card-hover);
    box-shadow: 0 10px 20px rgba(0,0,0,0.1) !important;
}

/* Animations */
@keyframes fadeIn {
    from { opacity: 0; transform: translateY(20px); }
    to { opacity: 1; transform: translateY(0); }
}

#task-content {
    transition: opacity 0.3s ease-in-out;
    animation: fadeIn 0.5s ease-out;
}

/* Hints */
.hint-card {
    border-left-width: 5px !important;
}

/* Scrollbar styling */
::-webkit-scrollbar {
    width: 8px;
}
::-webkit-scrollbar-track {
    background: #f1f1f1;
}
::-webkit-scrollbar-thumb {
    background: #cbd5e1;
    border-radius: 4px;
}
::-webkit-scrollbar-thumb:hover {
    background: #94a3b8;
}