/* ============================================
   LESSON ZERO - BASE STYLES
   Shared styles used across all pages
   ============================================ */

/* ============================================
   CSS CUSTOM PROPERTIES (VARIABLES)
   These define reusable colors throughout the site.
   To change a color globally, just update it here!
   ============================================ */
:root {
    --blue-deep: #0d1b2a;        /* Darkest blue - main background */
    --blue-dark: #1b3a4b;        /* Dark blue - secondary backgrounds */
    --blue-mid: #2d5a7b;         /* Medium blue - accents */
    --blue-bright: #4a90b8;      /* Bright blue - highlights */
    --blue-light: #a8d0e6;       /* Light blue - text on dark backgrounds */
    --white: #f8fafc;            /* Off-white for main text */
    --cream: #fefdfb;            /* Cream color for light sections */
    --yellow-highlight: #facc15; /* Yellow for text highlights */
    --yellow-accent: #facc15;    /* Yellow for buttons and accents */
    --grid-line: rgba(74, 144, 184, 0.15); /* Semi-transparent grid lines */
}

/* Reset default browser styles for consistency across browsers */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box; /* Makes width/height include padding and border */
}

/* Enable smooth scrolling when clicking anchor links */
html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Archivo', sans-serif;
    background: var(--blue-deep);
    color: var(--white);
    overflow-x: hidden; /* Prevent horizontal scrollbar */
}

body.modal-open {
    overflow: hidden;
}

/* ============================================
   TYPOGRAPHY
   ============================================ */

/* Yellow highlight background for emphasized words */
.highlight {
    display: inline;
    background-color: var(--yellow-highlight);
    padding: 0.02em 0.2em 0.18em 0.2em; /* Precise padding for visual balance */
    margin: 0 -0.05em;       /* Slight negative margin to compensate for padding */
}

/* Small label above headings (e.g., "THE PROBLEM") */
.section-label {
    display: inline-block;
    font-size: 0.7rem;
    font-weight: 600;
    letter-spacing: 0.2em;   /* Wide spacing for uppercase text */
    text-transform: uppercase;
    color: var(--yellow-accent);
    margin-bottom: 1rem;
}

/* Main section headings */
.section-heading {
    font-family: rockwell, serif;
    font-size: clamp(1.75rem, 4vw, 2.5rem); /* Responsive size */
    font-weight: 700;
    line-height: 1.2;        /* Tight line height for large text */
    margin-bottom: 1.25rem;
    color: var(--white);
}

/* Body text paragraphs */
.section-text {
    font-size: 1rem;
    line-height: 1.75;       /* Comfortable reading line height */
    color: var(--blue-light);
}

/* Add space between consecutive paragraphs */
/* CSS selector: .section-text + .section-text means
   "a .section-text that immediately follows another .section-text" */
.section-text + .section-text {
    margin-top: 1rem;
}

/* ============================================
   NAVIGATION
   ============================================ */

.main-nav {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    z-index: 10;              /* Layer 10: Above all page content */
    transition: background-color 0.3s ease, backdrop-filter 0.3s ease;
}

/* Transparent nav on homepage (when at top of page) */
.main-nav.transparent {
    background-color: transparent;
}

/* Solid nav (on scroll or on other pages) */
.main-nav.solid {
    background-color: rgba(13, 27, 42, 0.95);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--grid-line);
}

.nav-container {
    max-width: 1400px;
    margin: 0 auto;
    padding: 1.5rem 2rem;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.nav-logo {
    font-family: rockwell, serif;
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--white);
    text-decoration: none;
    transition: color 0.3s ease;
}

.nav-logo:hover {
    color: var(--yellow-accent);
}

.nav-menu {
    display: flex;
    gap: 2.5rem;
    list-style: none;
    margin: 0;
    padding: 0;
}

.nav-menu li {
    margin: 0;
}

.nav-menu a {
    color: var(--blue-light);
    text-decoration: none;
    font-size: 0.95rem;
    font-weight: 500;
    letter-spacing: 0.03em;
    transition: color 0.3s ease;
    position: relative;
}

.nav-menu a:hover {
    color: var(--white);
}

/* Active page indicator */
.nav-menu a.active {
    color: var(--yellow-accent);
}

.nav-menu a.active::after {
    content: '';
    position: absolute;
    bottom: -0.5rem;
    left: 0;
    width: 100%;
    height: 2px;
    background-color: var(--yellow-accent);
}

/* Mobile menu toggle button */
.mobile-menu-toggle {
    display: none;
    background: none;
    border: none;
    color: var(--white);
    font-size: 1.5rem;
    cursor: pointer;
    padding: 0.5rem;
    line-height: 1;
}

/* Mobile menu close button - hidden on desktop */
.mobile-menu-close {
    display: none;
}

/* Mobile styles */
@media (max-width: 768px) {
    .nav-container {
        padding: 1rem 1.5rem;
    }

    .mobile-menu-toggle {
        display: block;
    }

    .nav-menu {
        position: fixed;
        top: 0;
        right: -100%;
        width: 70%;
        max-width: 300px;
        height: 100vh;
        background-color: var(--blue-deep);
        flex-direction: column;
        gap: 0;
        padding: 5rem 2rem 2rem;
        transition: right 0.3s ease;
        border-left: 1px solid var(--grid-line);
    }

    .nav-menu.active {
        right: 0;
    }

    .nav-menu li {
        border-bottom: 1px solid var(--grid-line);
    }

    .nav-menu a {
        display: block;
        padding: 1.25rem 0;
        font-size: 1.1rem;
    }

    .nav-menu a.active::after {
        display: none;
    }

    /* Close button for mobile menu */
    .mobile-menu-close {
        display: none;
    }

    .nav-menu.active .mobile-menu-close {
        display: block;
        position: absolute;
        top: 1.5rem;
        right: 1.5rem;
        font-size: 1.5rem;
        color: var(--blue-light);
        cursor: pointer;
        background: none;
        border: none;
        padding: 0.5rem;
        line-height: 1;
    }
}

/* ============================================
   BUTTONS
   ============================================ */

.cta-button {
    display: inline-flex;
    align-items: center;
    gap: 0.75rem;
    background: var(--yellow-accent);
    color: var(--blue-deep);
    font-family: 'Archivo', sans-serif;
    font-size: 1rem;
    font-weight: 600;
    letter-spacing: 0.05em;
    text-decoration: none;
    padding: 1.25rem 2.5rem;
    border: none;
    cursor: pointer;
    transition: all 0.3s ease;
}

.cta-button:hover {
    background: #fde047;
    transform: translateY(-2px);
    box-shadow: 0 8px 30px rgba(250, 204, 21, 0.3);
}

.cta-button svg {
    transition: transform 0.3s ease;
}

.cta-button:hover svg {
    transform: translateX(4px);
}

/* ============================================
   FOOTER
   ============================================ */

footer {
    background: var(--blue-deep);
    border-top: 1px solid var(--grid-line);
    padding: 3rem 2rem;
    text-align: center;
    position: relative;
    z-index: 3;
}

.footer-logo {
    font-family: rockwell, serif;
    font-weight: 700;
    font-size: 1.5rem;
    margin-bottom: 1rem;
}

.footer-text {
    font-size: 0.875rem;
    color: var(--blue-mid);
}

/* ============================================
   UTILITY CLASSES
   ============================================ */

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 2rem;
}

/* ============================================
   VIDEO CARD COMPONENTS
   Shared video grid and card styles
   ============================================ */

.video-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
    max-width: 1200px;
    margin: 0 auto;
}

.video-card {
    position: relative;
    aspect-ratio: 16/9;
    overflow: hidden;
    cursor: pointer;
    box-shadow: 0 4px 20px rgba(13, 27, 42, 0.15);
    transition: transform 0.4s ease, box-shadow 0.4s ease;
}

.video-card:hover {
    transform: translateY(-8px);
    box-shadow: 0 12px 40px rgba(13, 27, 42, 0.25);
}

.video-card-overlay {
    position: absolute;
    bottom: 0;
    left: 0;
    right: 0;
    padding: 2rem 1.5rem 1.5rem;
    background: linear-gradient(transparent, rgba(13, 27, 42, 0.9));
    color: var(--white);
}

.video-card-title {
    font-family: rockwell, serif;
    font-weight: 700;
    font-size: 1.25rem;
    margin-bottom: 0.25rem;
}

.video-card-subtitle {
    font-size: 0.875rem;
    color: var(--blue-light);
}

.video-card video,
.video-card img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    transition: transform 0.6s ease;
}

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

/* Play button overlay on video cards */
.video-thumb-play {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    transition: transform 0.3s ease, opacity 0.3s ease;
    opacity: 0.85;
    pointer-events: none;
    z-index: 2;
}

.video-card:hover .video-thumb-play,
.video-thumb:hover .video-thumb-play {
    transform: translate(-50%, -50%) scale(1.1);
    opacity: 1;
}

@media (max-width: 768px) {
    .video-grid {
        grid-template-columns: 1fr;
    }
}

/* ============================================
   VIDEO LIGHTBOX MODAL
   Full-screen overlay with centered YouTube player
   ============================================ */
.video-modal {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: 100;
    display: flex;
    align-items: center;
    justify-content: center;
    visibility: hidden;
    pointer-events: none;
}

.video-modal.active {
    visibility: visible;
    pointer-events: auto;
}

.video-modal-backdrop {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.92);
    opacity: 0;
    transition: opacity 0.4s ease;
}

.video-modal.active .video-modal-backdrop {
    opacity: 1;
}

.video-modal-content {
    position: relative;
    width: 90%;
    max-width: 1100px;
    opacity: 0;
    transform: scale(0.95);
    transition: opacity 0.4s cubic-bezier(0.16, 1, 0.3, 1),
                transform 0.4s cubic-bezier(0.16, 1, 0.3, 1);
    transition-delay: 0.05s;
}

.video-modal.active .video-modal-content {
    opacity: 1;
    transform: scale(1);
}

.video-modal-player {
    position: relative;
    aspect-ratio: 16/9;
    width: 100%;
    background: #000;
}

.video-modal-player iframe {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    border: 0;
}

.video-modal-close {
    position: absolute;
    top: -3rem;
    right: 0;
    background: none;
    border: none;
    color: rgba(255, 255, 255, 0.7);
    font-size: 2rem;
    cursor: pointer;
    padding: 0.5rem;
    line-height: 1;
    transition: color 0.3s ease, transform 0.3s ease;
}

.video-modal-close:hover {
    color: #fff;
    transform: scale(1.15);
}

@media (max-width: 768px) {
    .video-modal-content {
        width: 95%;
    }

    .video-modal-close {
        top: -2.5rem;
        font-size: 1.75rem;
    }
}