.challenge {
    padding: 4rem 0;
    background-color: #f8f9fa;
}

.challenge-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
    max-width: 1000px;
    margin: 0 auto;
}

.challenge-card {
    background: white;
    border-radius: 10px;
    padding: 1.5rem;
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.1);
    transition: transform 0.3s ease;
    display: flex;
    flex-direction: column;
}

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

.video-thumbnail {
    position: relative;
    border-radius: 8px;
    overflow: hidden;
    margin-bottom: 1rem;
}

.video-thumbnail img {
    width: 100%;
    height: 180px;
    object-fit: cover;
    transition: transform 0.3s ease;
}

.video-thumbnail:hover img {
    transform: scale(1.05);
}

.play-overlay {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 60px;
    height: 60px;
    background: rgba(231, 76, 60, 0.9);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-size: 1.5rem;
    opacity: 0;
    transition: opacity 0.3s ease;
}

.video-thumbnail:hover .play-overlay {
    opacity: 1;
}

.next-event {
    background: linear-gradient(135deg, #2c3e50 0%, #34495e 100%);
    color: white;
    position: relative;
    overflow: hidden;
}

.next-event::before {
    content: '';
    position: absolute;
    top: 0;
    right: 0;
    width: 100px;
    height: 100px;
    background: rgba(243, 156, 18, 0.1);
    border-radius: 50%;
    transform: translate(30px, -30px);
}

.event-header {
    display: flex;
    align-items: center;
    margin-bottom: 1.5rem;
}

.event-header i {
    font-size: 2rem;
    color: #f39c12;
    margin-right: 1rem;
}

.event-header h3 {
    color: white;
    margin: 0;
    font-size: 1.5rem;
}

.event-details {
    margin-bottom: 1.5rem;
}

.event-details > div {
    display: flex;
    align-items: center;
    margin-bottom: 0.5rem;
    font-size: 0.95rem;
}

.event-details i {
    width: 20px;
    margin-right: 0.75rem;
    color: #f39c12;
}

.event-description {
    color: #ecf0f1;
    line-height: 1.6;
    margin-bottom: 1.5rem;
    font-size: 0.95rem;
}

.event-actions {
    display: flex;
    gap: 1rem;
    margin-bottom: 1rem;
    flex-wrap: wrap;
}

.registration-status {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding-top: 1rem;
    border-top: 1px solid rgba(255, 255, 255, 0.2);
}

.status-open {
    background: #27ae60;
    color: white;
    padding: 0.3rem 0.8rem;
    border-radius: 20px;
    font-size: 0.8rem;
    font-weight: 600;
}

.slots-available {
    color: #f39c12;
    font-size: 0.8rem;
    font-weight: 500;
}

.btn {
    display: inline-block;
    padding: 0.6rem 1.2rem;
    text-decoration: none;
    border-radius: 5px;
    font-weight: 600;
    transition: all 0.3s ease;
    border: 2px solid transparent;
    text-align: center;
    font-size: 0.9rem;
}

.btn-primary {
    background: #e74c3c;
    color: white;
    border-color: #e74c3c;
}

.btn-primary:hover {
    background: #c0392b;
    border-color: #c0392b;
    transform: translateY(-2px);
}

.btn-outline {
    background: #2c3e50;
    color: white;
    border-color: #B4B4B4;
}

.btn-outline:hover {
    background: #2c3e50;
    color: white;
    transform: translateY(-2px);
}

.next-event .btn-outline {
    color: white;
    border-color: white;
}

.next-event .btn-outline:hover {
    background: white;
    color: #2c3e50;
}

@media (max-width: 768px) {
    .challenge-grid {
        grid-template-columns: 1fr;
        gap: 1.5rem;
    }

    .event-actions {
        flex-direction: column;
    }

    .btn {
        width: 100%;
    }

    .registration-status {
        flex-direction: column;
        gap: 0.5rem;
        text-align: center;
    }

    .video-thumbnail img {
        height: 150px;
    }
}