:root {
    --primary-color: #667eea;
    --secondary-color: #764ba2;
    --success-color: #28a745;
    --danger-color: #dc3545;
    --warning-color: #ffc107;
    --info-color: #17a2b8;
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: #f8f9fa;
    min-height: 100vh;
}

/* Navbar */
.navbar {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%);
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
}

.navbar-brand {
    font-weight: bold;
    font-size: 1.3rem;
}

.nav-link {
    font-weight: 500;
    transition: all 0.3s;
}

.nav-link:hover {
    transform: translateY(-2px);
}

.nav-link.active {
    background: rgba(255,255,255,0.2);
    border-radius: 5px;
}

/* Cards */
.card {
    border: none;
    border-radius: 15px;
    transition: transform 0.3s;
}

.card:hover {
    transform: translateY(-5px);
}

/* Table horizontal scroll */
.table-responsive {
    position: relative;
    border-radius: 10px;
    box-shadow: 0 4px 6px rgba(0,0,0,0.1);
}

.table-responsive::-webkit-scrollbar {
    height: 8px;
}

.table-responsive::-webkit-scrollbar-track {
    background: #f1f1f1;
    border-radius: 4px;
}

.table-responsive::-webkit-scrollbar-thumb {
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    border-radius: 4px;
}

.table-responsive::-webkit-scrollbar-thumb:hover {
    background: linear-gradient(135deg, #5a6fd8, #6a4190);
}

/* Add scroll indicator */
.table-responsive::after {
    content: "← Scroll to see more columns →";
    position: absolute;
    bottom: -25px;
    left: 50%;
    transform: translateX(-50%);
    font-size: 12px;
    color: #666;
    font-style: italic;
    white-space: nowrap;
    opacity: 0.7;
}

.card-header {
    border-radius: 15px 15px 0 0 !important;
    border: none;
}

.bg-gradient {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%);
}

/* Stats Cards */
.stats-card {
    border-left: 4px solid var(--primary-color);
}

.stats-card h3 {
    font-size: 2rem;
    font-weight: bold;
    color: var(--primary-color);
}

/* Table */
.table {
    border-radius: 10px;
    overflow: hidden;
}

.table thead th {
    border: none;
    font-weight: 600;
    text-transform: uppercase;
    font-size: 0.85rem;
}

/* Table header gradient - refined styling with strong specificity */
#participantsTable thead,
#participantsTable.table > thead {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%) !important;
}

#participantsTable.table > thead > tr > th,
#participantsTable thead th,
#participantsTable thead th.sorting,
#participantsTable thead th.sorting_asc,
#participantsTable thead th.sorting_desc {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%) !important;
    color: #fff !important;
    border-bottom: 0 !important;
    box-shadow: inset 0 -2px 0 rgba(255,255,255,0.15), 0 4px 6px rgba(0,0,0,0.08) !important;
}

/* Improve visibility of sorting indicators on dark header */
#participantsTable thead th.sorting::before,
#participantsTable thead th.sorting::after,
#participantsTable thead th.sorting_asc::before,
#participantsTable thead th.sorting_asc::after,
#participantsTable thead th.sorting_desc::before,
#participantsTable thead th.sorting_desc::after {
    color: rgba(255,255,255,0.85) !important;
    opacity: 1 !important;
}

.table-hover tbody tr:hover {
    background-color: rgba(102, 126, 234, 0.1);
    cursor: pointer;
}

/* Buttons */
.btn {
    border-radius: 8px;
    padding: 8px 20px;
    font-weight: 500;
    transition: all 0.3s;
}

.btn-primary {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%);
    border: none;
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 5px 15px rgba(102, 126, 234, 0.4);
}

.btn-success {
    background: var(--success-color);
    border: none;
}

.btn-success:hover {
    background: #218838;
    transform: translateY(-2px);
}

.btn-danger {
    background: var(--danger-color);
    border: none;
}

.btn-danger:hover {
    background: #c82333;
    transform: translateY(-2px);
}

.btn-warning {
    background: var(--warning-color);
    border: none;
    color: #000;
}

.btn-warning:hover {
    background: #e0a800;
    transform: translateY(-2px);
}

/* Form Controls */
.form-control {
    border-radius: 8px;
    border: 2px solid #e0e0e0;
    padding: 10px 15px;
    transition: all 0.3s;
}

.form-control:focus {
    border-color: var(--primary-color);
    box-shadow: 0 0 0 0.2rem rgba(102, 126, 234, 0.25);
}

.form-label {
    font-weight: 600;
    color: #495057;
    margin-bottom: 8px;
}

/* Upload Area */
.upload-area {
    border: 3px dashed #dee2e6;
    border-radius: 15px;
    padding: 50px 30px;
    text-align: center;
    transition: all 0.3s;
    background: #f8f9fa;
}

.upload-area:hover {
    border-color: var(--primary-color);
    background: rgba(102, 126, 234, 0.05);
}

/* Badges */
.badge {
    padding: 6px 12px;
    border-radius: 6px;
    font-weight: 500;
}

/* Weight Loss Indicators */
.weight-loss-positive {
    color: var(--success-color);
    font-weight: bold;
}

.weight-loss-negative {
    color: var(--danger-color);
    font-weight: bold;
}

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

.card {
    animation: fadeIn 0.5s ease-in-out;
}

/* Responsive */
@media (max-width: 768px) {
    .navbar-brand {
        font-size: 1rem;
    }
    
    .stats-card h3 {
        font-size: 1.5rem;
    }
    
    .table {
        font-size: 0.85rem;
    }
}

/* DataTables customization */
.dataTables_wrapper .dataTables_filter input {
    border-radius: 8px;
    border: 2px solid #e0e0e0;
    padding: 6px 12px;
    margin-left: 10px;
}

.dataTables_wrapper .dataTables_length select {
    border-radius: 8px;
    border: 2px solid #e0e0e0;
    padding: 4px 8px;
}

.dataTables_wrapper .dataTables_paginate .paginate_button.current {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%) !important;
    border: none !important;
    color: white !important;
    border-radius: 5px;
}

.dataTables_wrapper .dataTables_paginate .paginate_button:hover {
    background: rgba(102, 126, 234, 0.1) !important;
    border: none !important;
    color: var(--primary-color) !important;
}

/* Modal */
.modal-content {
    border: none;
    border-radius: 15px;
    box-shadow: 0 10px 40px rgba(0,0,0,0.2);
}

.modal-header {
    border-radius: 15px 15px 0 0;
}

/* Action buttons in table */
.action-buttons {
    white-space: nowrap;
}

.action-buttons .btn {
    padding: 4px 10px;
    font-size: 0.85rem;
    margin: 0 2px;
}

/* Progress indicators */
.progress-indicator {
    display: inline-block;
    padding: 2px 8px;
    border-radius: 4px;
    font-size: 0.85rem;
    font-weight: 600;
}

.progress-excellent {
    background: #d4edda;
    color: #155724;
}

.progress-good {
    background: #d1ecf1;
    color: #0c5460;
}

.progress-average {
    background: #fff3cd;
    color: #856404;
}

.progress-poor {
    background: #f8d7da;
    color: #721c24;
}