/* Content Sections */
.content-sections {
    max-width: 750px;
    margin: 3rem auto;
    padding: 0 var(--spacing-md);
}

.hero-section {
    text-align: center;
    margin-bottom: var(--spacing-xl);
    padding: var(--spacing-lg);
    background: var(--surface-color);
    border-radius: var(--border-radius);
    box-shadow: var(--card-shadow);
    transition: all var(--transition-normal);
    position: relative;
    overflow: hidden;
}

.hero-section::before {
    content: '';
    position: absolute;
    inset: 0;
    background: var(--gradient);
    opacity: 0.03;
    z-index: 0;
    transition: opacity var(--transition-normal);
}

.hero-section:hover::before {
    opacity: 0.05;
}

.hero-section > * {
    position: relative;
    z-index: 1;
}

.hero-section:hover {
    box-shadow: var(--hover-shadow);
}

.hero-section h2 {
    background: var(--gradient);
    -webkit-background-clip: text;
    background-clip: text;
    color: transparent;
    font-size: 2rem;
    margin-bottom: 1rem;
}

/* Key Concepts Grid */
.key-concepts .grid {
    display: grid;
    gap: 1.5rem;
    margin: 2rem 0;
}

.concept-card {
    background: var(--surface-color);
    padding: var(--spacing-lg);
    border-radius: var(--border-radius);
    box-shadow: var(--card-shadow);
    transition: all var(--transition-normal);
    border: 1px solid rgba(37, 99, 235, 0.1);
    display: flex;
    flex-direction: column;
    align-items: center;
    text-align: center;
    position: relative;
    overflow: hidden;
}

.concept-card::before {
    content: '';
    position: absolute;
    inset: 0;
    background: var(--gradient);
    opacity: 0;
    transition: opacity var(--transition-normal);
    z-index: 0;
}

.concept-card:hover::before {
    opacity: 0.03;
}

.concept-card > * {
    position: relative;
    z-index: 1;
}

.concept-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--hover-shadow);
    border-color: rgba(37, 99, 235, 0.2);
    background: var(--surface-hover);
}

.concept-card .icon {
    width: 70px;
    height: 70px;
    margin-bottom: var(--spacing-md);
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 50%;
    background: var(--gradient);
    color: white;
    transition: all var(--transition-normal);
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
}

.concept-card:hover .icon {
    transform: translateY(-5px) scale(1.05);
    box-shadow: 0 6px 12px rgba(0, 0, 0, 0.15);
}

.concept-card .icon i {
    font-size: 2rem;
    filter: drop-shadow(0 2px 2px rgba(0, 0, 0, 0.1));
}

.concept-card h3 {
    color: var(--primary-color);
    font-size: 1.35rem;
    margin-bottom: 1rem;
    font-weight: 700;
    line-height: 1.3;
}

.concept-card p {
    color: var(--light-text);
    font-size: 1.1rem;
    margin-bottom: 0;
    line-height: 1.6;
}

/* Details/Summary Sections */
details {
    margin-bottom: 2rem;
    border: 1px solid rgba(37, 99, 235, 0.1);
    border-radius: var(--border-radius);
    background: var(--surface-color);
    transition: all var(--transition-normal);
    box-shadow: var(--card-shadow);
}

details[open] {
    box-shadow: var(--hover-shadow);
    border-color: rgba(37, 99, 235, 0.2);
}

summary {
    padding: 1.5rem 2rem;
    cursor: pointer;
    position: relative;
    font-weight: 600;
    font-size: 1.1rem;
    list-style: none;
    background: var(--surface-color);
    border-radius: var(--border-radius);
    transition: all var(--transition-normal);
    display: flex;
    align-items: center;
    gap: 1rem;
    color: var(--primary-color);
}

summary:hover {
    background: var(--hover-color);
}

summary::-webkit-details-marker {
    display: none;
}

summary::before {
    content: '\f054';
    font-family: 'Font Awesome 6 Free';
    font-weight: 900;
    font-size: 1em;
    transition: transform var(--transition-normal);
    color: var(--primary-color);
}

details[open] summary::before {
    transform: rotate(90deg);
}

.details-content {
    padding: var(--spacing-lg);
    animation: slideDown var(--transition-normal);
}

.details-content > * {
    animation: fadeIn var(--transition-normal) forwards;
    will-change: opacity, transform;
}

.details-content > *:nth-child(1) { animation-delay: 0.1s; }
.details-content > *:nth-child(2) { animation-delay: 0.2s; }
.details-content > *:nth-child(3) { animation-delay: 0.3s; }
.details-content > *:nth-child(4) { animation-delay: 0.4s; }
.details-content > *:nth-child(5) { animation-delay: 0.5s; }

/* Feature Lists */
.feature-list {
    list-style: none !important;
    padding-left: 0 !important;
}

.feature-list li {
    padding: var(--spacing-md) var(--spacing-md) var(--spacing-md) 3rem;
    position: relative;
    margin-bottom: var(--spacing-sm);
    background: var(--secondary-color);
    border-radius: var(--border-radius);
    transition: all var(--transition-normal);
    display: flex;
    align-items: center;
    gap: 0.6rem;
    font-size: 1rem;
}

.feature-list li::before {
    font-family: 'Font Awesome 6 Free';
    font-weight: 900;
    position: absolute;
    left: 1.25rem;
    font-size: 1.1rem;
}


.feature-list li[data-icon="times"]::before {
    content: '\f00d';
    color: var(--danger-color);
}

.feature-list li i {
    width: 6rem;
    height: 4rem;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    background: var(--gradient);
    color: white;
    border-radius: 50%;
    font-size: 1.6rem;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
    transition: all var(--transition-normal);
    margin-right: 0.9rem;
}

.feature-list li:hover i {
    transform: scale(1.1);
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.15);
}

.feature-list li strong {
    color: var(--primary-color);
    font-weight: 600;
}

.feature-list li:hover {
    background: var(--surface-color);
    transform: translateX(5px);
    box-shadow: var(--card-shadow);
}

/* Real World Example */
.real-world-example {
    background: linear-gradient(135deg, var(--hover-color), var(--surface-color));
    padding: var(--spacing-lg);
    border-radius: var(--border-radius);
    margin: var(--spacing-lg) 0;
    border-left: 3px solid var(--primary-color);
    position: relative;
    overflow: hidden;
    box-shadow: var(--card-shadow);
    transition: all var(--transition-normal);
}

.real-world-example:hover {
    box-shadow: var(--hover-shadow);
    transform: translateY(-2px);
}

.real-world-example::before {
    content: '\f0eb';
    font-family: 'Font Awesome 6 Free';
    font-weight: 900;
    position: absolute;
    top: -1rem;
    right: -1rem;
    font-size: 5rem;
    opacity: 0.1;
    transform: rotate(15deg);
    transition: transform var(--transition-normal);
}

.real-world-example:hover::before {
    transform: rotate(25deg);
}

.real-world-example h4 {
    color: var(--primary-color);
    margin-bottom: 1rem;
    font-size: 1.25rem;
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

.real-world-example h4 i {
    font-size: 1.2em;
    color: var(--primary-color);
    filter: drop-shadow(0 1px 2px rgba(0, 0, 0, 0.1));
}

/* Responsive Grid */
@media (min-width: 768px) {
    .key-concepts .grid {
        grid-template-columns: repeat(2, 1fr);
        align-items: stretch;
    }
    
    .concept-card {
        height: 100%;
        justify-content: center;
    }
}

@media (min-width: 1024px) {
    .key-concepts .grid {
        grid-template-columns: repeat(3, 1fr);
    }
}

@media (max-width: 480px) {
    .hero-section {
        padding: 1.5rem;
    }

    .concept-card {
        padding: 1.5rem;
    }

    .details-content {
        padding: 1.25rem;
    }

    .real-world-example {
        padding: 1.5rem;
    }
}