/* Challenges Section - Interactive Card Grid */
.challenges {
    background: linear-gradient(180deg, var(--bg-secondary) 0%, var(--bg-primary) 100%);
    padding: 6rem 0;
    position: relative;
}

/* Challenges Grid */
.challenges-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(340px, 1fr));
    gap: 2.5rem;
    max-width: 1400px;
    margin: 0 auto;
}

/* Challenge Card - Enhanced Design */
.challenge-card {
    background: var(--card-bg);
    border: 2px solid var(--card-border);
    border-radius: 28px;
    padding: 3rem 2.5rem;
    transition: all 0.5s cubic-bezier(0.4, 0, 0.2, 1);
    box-shadow: 0 4px 16px var(--shadow-sm);
    position: relative;
    overflow: hidden;
    backdrop-filter: blur(10px);
    display: flex;
    flex-direction: column;
}

/* Animated gradient border */
.challenge-card::before {
    content: '';
    position: absolute;
    inset: -2px;
    border-radius: 28px;
    padding: 2px;
    background: var(--gradient-accent);
    -webkit-mask: linear-gradient(#fff 0 0) content-box, linear-gradient(#fff 0 0);
    -webkit-mask-composite: xor;
    mask: linear-gradient(#fff 0 0) content-box, linear-gradient(#fff 0 0);
    mask-composite: exclude;
    opacity: 0;
    transition: opacity 0.4s ease;
    z-index: -1;
}

.challenge-card:hover::before {
    opacity: 1;
}

/* Floating effect */
.challenge-card::after {
    content: '';
    position: absolute;
    top: -50%;
    right: -50%;
    width: 200%;
    height: 200%;
    background: radial-gradient(circle, rgba(52, 152, 219, 0.1) 0%, transparent 70%);
    opacity: 0;
    transition: opacity 0.4s ease;
    pointer-events: none;
}

.challenge-card:hover::after {
    opacity: 1;
}

.challenge-card:hover {
    box-shadow: 0 24px 64px var(--shadow-2xl);
    transform: translateY(-10px) scale(1.02);
    border-color: var(--accent-primary);
}

.challenge-title {
    font-size: 1.5rem;
    margin-bottom: 1.25rem;
    color: var(--text-primary);
    font-weight: 800;
    line-height: 1.3;
    letter-spacing: -0.01em;
}

.challenge-card p {
    color: var(--text-muted);
    line-height: 1.8;
    font-size: 1.05rem;
    margin-bottom: 0;
    flex-grow: 1;
}

.challenge-projects {
    margin-top: 0;
    padding-top: 0;
    border-top: 2px solid transparent;
    opacity: 0;
    max-height: 0;
    overflow: hidden;
    transition: all 0.4s cubic-bezier(0.4, 0, 0.2, 1);
}

.challenge-card:hover .challenge-projects {
    margin-top: 2rem;
    padding-top: 1.5rem;
    border-top-color: var(--border-light);
    opacity: 1;
    max-height: 300px;
}

.challenge-projects h4 {
    font-size: 0.85rem;
    color: var(--text-light);
    margin-bottom: 1rem;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    font-weight: 700;
    opacity: 0;
    transform: translateY(-5px);
    transition: all 0.4s cubic-bezier(0.4, 0, 0.2, 1) 0.1s;
}

.challenge-card:hover .challenge-projects h4 {
    opacity: 1;
    transform: translateY(0);
}

.project-badges {
    display: flex;
    flex-wrap: wrap;
    gap: 0.65rem;
    opacity: 0;
    transform: translateY(-10px);
    transition: all 0.4s cubic-bezier(0.4, 0, 0.2, 1) 0.15s;
}

.challenge-card:hover .project-badges {
    opacity: 1;
    transform: translateY(0);
}

.project-badge {
    background: linear-gradient(135deg, rgba(52, 152, 219, 0.1) 0%, rgba(52, 152, 219, 0.05) 100%);
    color: var(--accent-primary);
    padding: 0.5rem 1rem;
    border-radius: 20px;
    font-size: 0.85rem;
    font-weight: 600;
    border: 1.5px solid rgba(52, 152, 219, 0.2);
    transition: all 0.3s ease;
}

.challenge-card:hover .project-badge {
    background: var(--gradient-accent);
    color: white;
    border-color: transparent;
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(52, 152, 219, 0.3);
}

/* Responsive */
@media (max-width: 1024px) {
    .challenges-grid {
        grid-template-columns: repeat(2, 1fr);
        gap: 2rem;
    }
}

@media (max-width: 768px) {
    .challenges {
        padding: 4rem 0;
    }
    
    .challenges-grid {
        grid-template-columns: 1fr;
        gap: 1.5rem;
    }
    
    .challenge-card {
        padding: 2rem 1.5rem;
    }
    
    .challenge-title {
        font-size: 1.35rem;
    }
}