/* ==========================================================================
   1. Base Reset & Typography Setup
   ========================================================================== */

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

body {
    font-family: Arial, Helvetica, sans-serif;
    background-color: #f8fafc;
    color: #111;
    line-height: 1.5;
}

/* Page Width Restraint Container */
.content-container {
    max-width: 900px;
    margin: 0 auto;
    padding: 20px 15px;
}

/* ==========================================================================
   2. Header & Navigation Structure
   ========================================================================== */

.main-header {
    text-align: center;
    background-color: #e0ebff;
    padding-top: 15px;
}

.main-header h1 {
    color: #0000d6;
    font-size: 1.8rem;
    font-weight: bold;
    margin-bottom: 12px;
}

.nav-bar {
    background-color: #333333;
    padding: 10px 0;
    display: flex;
    justify-content: center;
    gap: 30px;
}

.nav-bar a {
    color: #ffffff;
    text-decoration: underline;
    font-weight: bold;
    font-size: 0.95rem;
}

.subtitle {
    font-size: 0.85rem;
    color: #333;
    padding: 12px 10px;
    background-color: #e0ebff;
}

/* ==========================================================================
   3. Demonstration Sections
   ========================================================================== */

.example-section {
    margin-top: 30px;
    margin-bottom: 40px;
}

/* Section Divider Bar Header */
.section-title {
    color: #00008b;
    font-size: 1.4rem;
    text-align: center;
    padding-bottom: 5px;
    border-bottom: 2px solid #00008b;
    margin-bottom: 12px;
}

.section-desc {
    font-size: 0.85rem;
    color: #222;
    margin-bottom: 20px;
}

/* ==========================================================================
   4. Feature 1: CSS Grid Implementation
   ========================================================================== */

.grid-container {
    display: grid;
    /* 3-column setup on standard desktops */
    grid-template-columns: repeat(3, 1fr);
    gap: 15px;
}

.card {
    border: 1px solid #777777;
    background-color: #ffffff;
    padding: 15px;
    text-align: center;
    display: flex;
    flex-direction: column;
    align-items: center;
}

.card h3 {
    font-size: 0.95rem;
    margin-bottom: 8px;
    color: #000;
}

.card p {
    font-size: 0.8rem;
    color: #333;
    margin-bottom: 15px;
}

.card img {
    width: 100%;
    height: 180px;
    object-fit: cover;
    display: block;
}

/* ==========================================================================
   5. Feature 2: Fluid Image Scalability
   ========================================================================== */

.large-image-wrapper {
    width: 100%;
    text-align: center;
}

/* Image never exceeds container width */
.responsive-large-img {
    max-width: 100%;
    height: auto;
    display: block;
    margin: 0 auto;
}

/* ==========================================================================
   6. Feature 3: Flexbox Module Arrangement
   ========================================================================== */

.flexbox-container {
    display: flex;
    justify-content: space-between;
    gap: 15px;
    flex-wrap: wrap;
}

.flex-box {
    flex: 1;
    min-width: 150px;
    border: 1px solid #777777;
    background-color: #ffffff;
    padding: 12px;
    text-align: center;
    font-size: 0.85rem;
}

/* ==========================================================================
   7. Page Footer
   ========================================================================== */

.main-footer {
    text-align: center;
    font-size: 0.75rem;
    color: #555;
    padding: 20px 0 30px;
}

/* ==========================================================================
   8. Media Queries for Screen Breakpoints
   ========================================================================== */

@media screen and (max-width: 768px) {
    .grid-container {
        /* Collapse grid into single column for tablet/mobile viewports */
        grid-template-columns: 1fr;
    }

    .flexbox-container {
        flex-direction: column;
    }
}