/* ==========================================================================
 * DSTAIR — About Page
 * Grid background, premium info cards, concept/blueprint card systems,
 * mobile carousel, and typography overrides.
 * ========================================================================== */


/* --------------------------------------------------------------------------
 * § 1. BACKGROUND — SUBTLE GRID MESH
 * -------------------------------------------------------------------------- */
.about-background {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: var(--z-background);
    background:
        radial-gradient(circle at 10% 20%, rgba(var(--color-primary-rgb), 0.1) 0%, transparent 40%),
        radial-gradient(circle at 90% 80%, rgba(var(--color-highlight-rgb), 0.05) 0%, transparent 40%),
        linear-gradient(rgba(var(--color-dark-rgb), 0.95), rgba(var(--color-dark-rgb), 0.95)),
        repeating-linear-gradient(0deg, transparent, transparent 49px, rgba(255, 255, 255, 0.025) 50px),
        repeating-linear-gradient(90deg, transparent, transparent 49px, rgba(255, 255, 255, 0.025) 50px);
    background-size: 100% 100%, 100% 100%, 100% 100%, 100px 100px, 100px 100px;
}

.border-accent-left {
    border-left: 3px solid var(--color-accent);
}

.step-number {
    font-family: var(--font-mono);
    color: var(--color-highlight);
    font-weight: 700;
    opacity: 0.5;
}


/* --------------------------------------------------------------------------
 * § 2. PREMIUM SECTION WRAPPER
 * -------------------------------------------------------------------------- */
:root {
    --dstair-color-primary-blue: var(--color-primary);
    --dstair-color-accent-orange: var(--color-accent);
    --dstair-color-highlight-lime: var(--color-highlight);
    --dstair-color-white: var(--white);
    --dstair-color-offwhite: #F8FAFC;
}

.dstair-premium-section-wrapper {
    font-family: var(--font-sans);
    background-color: transparent !important;
    color: var(--color-primary);
    overflow: hidden;
    position: relative;
    border-radius: var(--radius-lg);
}


/* --------------------------------------------------------------------------
 * § 3. BACKGROUND TEXTURE
 * -------------------------------------------------------------------------- */
.dstair-background-texture-layer {
    background-image: radial-gradient(var(--color-primary) 1px, transparent 1px);
    background-size: 40px 40px;
    opacity: 0.04;
}


/* --------------------------------------------------------------------------
 * § 4. INFORMATIONAL MODULE CARDS
 * -------------------------------------------------------------------------- */
.dstair-informational-module-card {
    background: var(--white);
    border: 1px solid rgba(var(--color-primary-rgb), 0.08);
    transition: all 0.4s var(--ease-spring);
    position: relative;
    overflow: hidden;
    display: flex;
    flex-direction: column;
}

.dstair-informational-module-card:hover {
    transform: translateY(-6px);
    box-shadow: 0 20px 40px -10px rgba(var(--color-primary-rgb), 0.15);
    border-color: var(--color-primary);
}

/* Orange accent bar — reveals on hover */
.dstair-visual-accent-bar {
    position: absolute;
    top: 0;
    left: 0;
    width: 4px;
    height: 100%;
    background: var(--color-accent);
    opacity: 0;
    transition: opacity var(--transition-base);
}

.dstair-informational-module-card:hover .dstair-visual-accent-bar {
    opacity: 1;
}


/* --------------------------------------------------------------------------
 * § 5. TYPOGRAPHY
 * -------------------------------------------------------------------------- */
.dstair-typography-heading-serif {
    font-family: var(--font-serif);
}

.dstair-text-muted {
    color: var(--white-60);
}


/* --------------------------------------------------------------------------
 * § 6. CARD VARIANTS
 * -------------------------------------------------------------------------- */

/* Blue background variant */
.dstair-module-variant-primary-blue {
    background-color: var(--color-primary);
    color: var(--white);
}

.dstair-module-variant-primary-blue .dstair-text-muted {
    color: var(--white-80);
}

.dstair-module-variant-primary-blue .dstair-visual-accent-bar {
    background: var(--color-highlight);
}

/* Institutional logo grid */
.dstair-institutional-logo-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 1rem;
    opacity: 0.6;
}


/* --------------------------------------------------------------------------
 * § 7. MOBILE CAROUSEL
 * -------------------------------------------------------------------------- */
.dstair-mobile-horizontal-scroll-container {
    scroll-snap-type: x mandatory;
    -webkit-overflow-scrolling: touch;
    scrollbar-width: none;
}

.dstair-mobile-horizontal-scroll-container::-webkit-scrollbar {
    display: none;
}

.dstair-mobile-snap-item {
    scroll-snap-align: center;
}


/* --------------------------------------------------------------------------
 * § 8. NAVIGATION ARROWS
 * -------------------------------------------------------------------------- */
.dstair-navigation-arrow-circle {
    width: 40px;
    height: 40px;
    border-radius: 50%;
    border: 1px solid var(--color-primary);
    color: var(--color-primary);
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all var(--transition-base);
    cursor: pointer;
    background: rgba(255, 255, 255, 0.85);
}

.dstair-navigation-arrow-circle:hover {
    background: var(--color-primary);
    color: var(--white);
    transform: scale(1.08);
}


/* --------------------------------------------------------------------------
 * § 9. LIME HIGHLIGHT TAG
 * -------------------------------------------------------------------------- */
.dstair-tag-highlight-lime {
    background-color: var(--color-highlight);
    color: var(--color-primary);
    font-weight: 700;
    letter-spacing: -0.02em;
}


/* --------------------------------------------------------------------------
 * § 10. CONCEPT CARDS (What is / Difference sections)
 * -------------------------------------------------------------------------- */
.dstair-concept-card {
    background: rgba(255, 255, 255, 0.03);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
    border: 1px solid var(--white-10);
    border-radius: var(--radius-lg);
    padding: 2.5rem;
    position: relative;
    overflow: hidden;
    transition: all 0.35s var(--ease-spring);
}

.dstair-concept-card:hover {
    background: rgba(255, 255, 255, 0.06);
    border-color: var(--white-20);
    transform: translateY(-3px);
    box-shadow: 0 12px 32px -8px rgba(0, 0, 0, 0.35);
}

/* Top-edge light sweep */
.dstair-concept-card::after {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 1px;
    background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.5), transparent);
    opacity: 0;
    transition: opacity var(--transition-base);
}

.dstair-concept-card:hover::after {
    opacity: 1;
}


/* --------------------------------------------------------------------------
 * § 11. BLUEPRINT CARDS (How it Works section)
 * -------------------------------------------------------------------------- */
.dstair-blueprint-card {
    background: linear-gradient(145deg,
            rgba(var(--color-dark-rgb), 0.4),
            rgba(var(--color-dark-rgb), 0.7));
    backdrop-filter: blur(5px);
    -webkit-backdrop-filter: blur(5px);
    border: 1px solid rgba(var(--color-primary-rgb), 0.2);
    border-radius: var(--radius-md);
    padding: 2rem 1.5rem;
    position: relative;
    transition: all 0.3s var(--ease-smooth);
    display: flex;
    flex-direction: column;
}

.dstair-blueprint-card:hover {
    border-color: var(--color-highlight);
    box-shadow:
        0 0 0 1px rgba(var(--color-highlight-rgb), 0.1),
        0 12px 24px -5px rgba(0, 0, 0, 0.25);
    transform: translateY(-3px);
}

/* Corner markers for technical feel */
.dstair-blueprint-marker {
    position: absolute;
    width: 6px;
    height: 6px;
    border: 1px solid var(--white-20);
    transition: border-color var(--transition-base);
}

.dstair-blueprint-marker-tl {
    top: 8px;
    left: 8px;
    border-right: 0;
    border-bottom: 0;
}

.dstair-blueprint-marker-tr {
    top: 8px;
    right: 8px;
    border-left: 0;
    border-bottom: 0;
}

.dstair-blueprint-marker-bl {
    bottom: 8px;
    left: 8px;
    border-right: 0;
    border-top: 0;
}

.dstair-blueprint-marker-br {
    bottom: 8px;
    right: 8px;
    border-left: 0;
    border-top: 0;
}

.dstair-blueprint-card:hover .dstair-blueprint-marker {
    border-color: var(--color-highlight);
}

/* Watermark step number */
.dstair-blueprint-step {
    font-family: var(--font-mono);
    font-size: 4rem;
    font-weight: 800;
    color: rgba(255, 255, 255, 0.025);
    position: absolute;
    top: -0.5rem;
    right: 0.5rem;
    line-height: 1;
    pointer-events: none;
    transition: all 0.4s var(--ease-out);
    z-index: 0;
}

.dstair-blueprint-card:hover .dstair-blueprint-step {
    color: rgba(255, 255, 255, 0.08);
    transform: translateY(5px);
}

.dstair-blueprint-content {
    position: relative;
    z-index: 1;
}