:root {
    --primary-color: #007bff;
    --primary-hover: #0056b3;
    --secondary-color: #6c757d;
    --success-color: #28a745;
    --success-hover: #1e7e34;
    --danger-color: #dc3545;
    --warning-color: #ffc107;
    --light-color: #f8f9fa;
    --dark-color: #343a40;
    --background: #f5f7fa;
    --surface: #ffffff;
    --border: #dee2e6;
    --text-primary: #212529;
    --text-secondary: #6c757d;
    --text-muted: #9ca3af;
    --shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 4px 16px rgba(0, 0, 0, 0.1);
    --border-radius: 8px;
    --font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
}

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

body {
    font-family: var(--font-family);
    background-color: var(--background);
    color: var(--text-primary);
    line-height: 1.6;
}

.container {
    min-height: 100vh;
}

/* Header */
.header {
    background: linear-gradient(135deg, var(--primary-color), var(--primary-hover));
    color: white;
    padding: 2rem 0;
    text-align: center;
    box-shadow: var(--shadow-lg);
}

.logo {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 1rem;
}

.logo i {
    font-size: 2.5rem;
}

.logo h1 {
    font-size: 2rem;
    font-weight: 600;
}

/* Main Layout */
.main {
    max-width: 800px;
    margin: 0 auto;
    padding: 3rem 2rem;
}

/* Card Styles */
.card {
    background: var(--surface);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-lg);
    padding: 2rem;
    margin-bottom: 2rem;
}

.card h2 {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    margin-bottom: 1.5rem;
    color: var(--text-primary);
    font-size: 1.5rem;
    font-weight: 600;
}

/* Form Styles */
.form-group {
    margin-bottom: 1.5rem;
}

.form-group label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 500;
    color: var(--text-primary);
}

.form-group input,
.form-group textarea,
.form-group select {
    width: 100%;
    padding: 0.75rem;
    border: 2px solid var(--border);
    border-radius: var(--border-radius);
    font-family: var(--font-family);
    font-size: 1rem;
    transition: border-color 0.2s, box-shadow 0.2s;
}

.form-group input:focus,
.form-group textarea:focus,
.form-group select:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(0, 123, 255, 0.1);
}

.form-group textarea {
    resize: vertical;
    min-height: 100px;
}

/* Button Styles */
.btn {
    padding: 0.75rem 1.5rem;
    border: none;
    border-radius: var(--border-radius);
    font-family: var(--font-family);
    font-size: 1rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s;
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    text-decoration: none;
    border: 2px solid transparent;
}

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

.btn-primary:hover {
    background: var(--primary-hover);
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

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

.btn-secondary:hover {
    background: #5a6268;
    transform: translateY(-2px);
}

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

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

.btn-outline {
    background: transparent;
    color: var(--text-primary);
    border: 2px solid var(--border);
}

.btn-outline:hover {
    background: var(--light-color);
    transform: translateY(-2px);
}

/* Results Section */
.results-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1.5rem;
    flex-wrap: wrap;
    gap: 1rem;
}

.results-actions {
    display: flex;
    gap: 0.75rem;
    flex-wrap: wrap;
}

.user-info {
    background: var(--light-color);
    padding: 1rem;
    border-radius: var(--border-radius);
    margin-bottom: 2rem;
    border-left: 4px solid var(--primary-color);
}

.user-info p {
    margin-bottom: 0.5rem;
}

.user-info p:last-child {
    margin-bottom: 0;
}

/* Challenge Cards */
.challenges-grid {
    display: grid;
    gap: 1.5rem;
    margin-bottom: 2rem;
}

.challenge-card {
    background: var(--surface);
    border: 2px solid var(--border);
    border-radius: var(--border-radius);
    padding: 1.5rem;
    transition: all 0.2s;
}

.challenge-card:hover {
    border-color: var(--primary-color);
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

.challenge-header {
    display: flex;
    justify-content: between;
    align-items: flex-start;
    margin-bottom: 1rem;
    gap: 1rem;
}

.challenge-title {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 0.5rem;
}

.challenge-type {
    background: var(--primary-color);
    color: white;
    padding: 0.25rem 0.75rem;
    border-radius: 20px;
    font-size: 0.875rem;
    font-weight: 500;
}

.challenge-description {
    color: var(--text-secondary);
    margin-bottom: 1rem;
    line-height: 1.5;
}

.challenge-meta {
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-size: 0.875rem;
    color: var(--text-muted);
}

.challenge-prize {
    font-weight: 600;
    color: var(--success-color);
    font-size: 1rem;
}

/* Actions */
.actions {
    display: flex;
    gap: 1rem;
    justify-content: center;
    flex-wrap: wrap;
}

/* Modal Styles */
.modal {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.5);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 1000;
}

.modal-content {
    background: var(--surface);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-lg);
    width: 90%;
    max-width: 500px;
    max-height: 80vh;
    overflow-y: auto;
}

.modal-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1.5rem;
    border-bottom: 1px solid var(--border);
}

.modal-header h3 {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    margin: 0;
}

.close-btn {
    background: none;
    border: none;
    font-size: 1.5rem;
    cursor: pointer;
    color: var(--text-muted);
    padding: 0.25rem;
    line-height: 1;
}

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

.modal-body {
    padding: 1.5rem;
}

.modal-footer {
    padding: 1.5rem;
    border-top: 1px solid var(--border);
    display: flex;
    gap: 1rem;
    justify-content: flex-end;
}

/* Loading Spinner */
.loading {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(255, 255, 255, 0.9);
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    z-index: 1000;
}

.spinner {
    width: 50px;
    height: 50px;
    border: 5px solid var(--border);
    border-top: 5px solid var(--primary-color);
    border-radius: 50%;
    animation: spin 1s linear infinite;
    margin-bottom: 1rem;
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}

.loading p {
    color: var(--text-secondary);
    font-size: 1.1rem;
}

/* Success Message */
.success-message {
    position: fixed;
    top: 2rem;
    right: 2rem;
    background: var(--success-color);
    color: white;
    padding: 1rem 1.5rem;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-lg);
    display: flex;
    align-items: center;
    gap: 0.75rem;
    z-index: 1000;
    animation: slideIn 0.3s ease-out;
}

@keyframes slideIn {
    from {
        transform: translateX(100%);
        opacity: 0;
    }
    to {
        transform: translateX(0);
        opacity: 1;
    }
}

/* Responsive Design */
@media (max-width: 768px) {
    .main {
        padding: 2rem 1rem;
    }
    
    .card {
        padding: 1.5rem;
    }
    
    .results-header {
        flex-direction: column;
        align-items: stretch;
    }
    
    .results-actions {
        justify-content: center;
    }
    
    .actions {
        flex-direction: column;
    }
    
    .modal-content {
        width: 95%;
        margin: 1rem;
    }
    
    .modal-footer {
        flex-direction: column;
    }
    
    .success-message {
        right: 1rem;
        left: 1rem;
    }
}