/* ==========================================================================
   Main Street Marketplace Toolkit — landing page styles.
   Pure CSS, no preprocessor. CSS custom properties mirror brand/tokens.json.
   Mobile-first; desktop refinements come in via min-width media queries.
   ========================================================================== */

:root {
    /* Colors */
    --color-primary:        #1B4F8A;
    --color-primary-light:  #2D6DB5;
    --color-primary-dark:   #0F3060;
    --color-accent:         #E85D26;
    --color-accent-light:   #F07A48;
    --color-success:        #2E7D32;
    --color-warning:        #F57C00;
    --color-danger:         #C62828;
    --color-neutral-100:    #FFFFFF;
    --color-neutral-200:    #F5F6F8;
    --color-neutral-300:    #E8EAED;
    --color-neutral-600:    #5F6368;
    --color-neutral-900:    #1A1A2E;

    /* Typography */
    --font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    --fs-base:  16px;
    --fs-sm:    14px;
    --fs-lg:    20px;
    --fs-xl:    28px;
    --fs-hero:  40px;

    /* Layout */
    --container-max: 1100px;
    --radius:        8px;
    --shadow:        0 2px 12px rgba(27, 79, 138, 0.08);
    --shadow-lg:     0 8px 32px rgba(27, 79, 138, 0.12);
}

/* --------------------------------------------------------------------------
   Reset / base
   -------------------------------------------------------------------------- */

*, *::before, *::after { box-sizing: border-box; }

html {
    scroll-behavior: smooth;
    text-size-adjust: 100%;
}

body {
    margin: 0;
    padding: 0;
    font-family: var(--font-family);
    font-size: var(--fs-base);
    line-height: 1.55;
    color: var(--color-neutral-900);
    background-color: var(--color-neutral-100);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

h1, h2, h3, h4 {
    margin: 0 0 0.5em;
    color: var(--color-neutral-900);
    letter-spacing: -0.015em;
    line-height: 1.2;
}

p { margin: 0 0 1em; }

a {
    color: var(--color-primary);
    text-decoration: none;
    transition: color 0.15s ease;
}

a:hover { color: var(--color-primary-dark); }

img { display: block; max-width: 100%; height: auto; }

ul, ol { padding: 0; margin: 0; list-style: none; }

.container {
    width: 100%;
    max-width: var(--container-max);
    margin: 0 auto;
    padding: 0 1.5rem;
}

/* --------------------------------------------------------------------------
   Buttons
   -------------------------------------------------------------------------- */

.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 0.75rem 1.4rem;
    font-family: var(--font-family);
    font-size: var(--fs-base);
    font-weight: 600;
    border-radius: var(--radius);
    border: 1.5px solid transparent;
    cursor: pointer;
    text-decoration: none;
    transition: background-color 0.15s ease, color 0.15s ease,
                border-color 0.15s ease, transform 0.05s ease;
    white-space: nowrap;
}

.btn:active { transform: translateY(1px); }

.btn-primary {
    background-color: var(--color-primary);
    color: var(--color-neutral-100);
    border-color: var(--color-primary);
}

.btn-primary:hover {
    background-color: var(--color-primary-dark);
    border-color: var(--color-primary-dark);
    color: var(--color-neutral-100);
}

.btn-outline {
    background-color: transparent;
    color: var(--color-primary);
    border-color: var(--color-primary);
}

.btn-outline:hover {
    background-color: var(--color-primary);
    color: var(--color-neutral-100);
}

.btn-on-dark {
    background-color: var(--color-neutral-100);
    color: var(--color-primary);
    border-color: var(--color-neutral-100);
}

.btn-on-dark:hover {
    background-color: rgba(255, 255, 255, 0.92);
    color: var(--color-primary-dark);
}

.btn-on-dark-outline {
    background-color: transparent;
    color: var(--color-neutral-100);
    border-color: rgba(255, 255, 255, 0.7);
}

.btn-on-dark-outline:hover {
    background-color: rgba(255, 255, 255, 0.10);
    color: var(--color-neutral-100);
    border-color: var(--color-neutral-100);
}

/* --------------------------------------------------------------------------
   Navbar
   -------------------------------------------------------------------------- */

.navbar {
    position: sticky;
    top: 0;
    z-index: 50;
    background-color: rgba(255, 255, 255, 0.94);
    backdrop-filter: saturate(180%) blur(8px);
    -webkit-backdrop-filter: saturate(180%) blur(8px);
    border-bottom: 1px solid var(--color-neutral-300);
}

.navbar-inner {
    max-width: var(--container-max);
    margin: 0 auto;
    padding: 0.85rem 1.5rem;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 1rem;
}

.brand {
    display: inline-flex;
    align-items: center;
    gap: 0.6rem;
    color: var(--color-primary);
    font-weight: 700;
    line-height: 1;
}

.brand-logo {
    height: 32px;
    width: auto;
    color: var(--color-primary);
    display: block;
}

.brand-name {
    font-size: 0.95rem;
    color: var(--color-neutral-900);
    letter-spacing: -0.01em;
}

.nav-links {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.nav-link {
    color: var(--color-neutral-600);
    font-size: 0.95rem;
    font-weight: 500;
}

.nav-link:hover { color: var(--color-primary-dark); }

.nav-cta {
    padding: 0.55rem 1rem;
    font-size: 0.95rem;
}

@media (max-width: 600px) {
    .brand-name { display: none; }
    .nav-link { display: none; }
    .nav-cta { padding: 0.5rem 0.9rem; }
}

/* --------------------------------------------------------------------------
   Hero
   -------------------------------------------------------------------------- */

.hero {
    position: relative;
    padding: 5rem 0 4rem;
    background:
        radial-gradient(circle at 20% 10%, rgba(45, 109, 181, 0.10) 0%, transparent 45%),
        radial-gradient(circle at 90% 100%, rgba(232, 93, 38, 0.07) 0%, transparent 50%),
        linear-gradient(180deg, var(--color-neutral-100) 0%, var(--color-neutral-200) 100%);
    overflow: hidden;
}

.hero-inner {
    text-align: center;
    max-width: 820px;
}

.eyebrow {
    display: inline-block;
    background-color: var(--color-neutral-100);
    color: var(--color-primary);
    border: 1px solid var(--color-neutral-300);
    font-size: var(--fs-sm);
    font-weight: 600;
    letter-spacing: 0.05em;
    text-transform: uppercase;
    padding: 0.4rem 0.9rem;
    border-radius: 999px;
    margin-bottom: 1.5rem;
}

.hero-headline {
    font-size: 2.25rem;
    font-weight: 700;
    line-height: 1.1;
    color: var(--color-neutral-900);
    margin-bottom: 1.25rem;
}

.hero-subhead {
    font-size: 1.1rem;
    color: var(--color-neutral-600);
    max-width: 640px;
    margin: 0 auto 2rem;
}

.hero-ctas {
    display: flex;
    gap: 0.85rem;
    justify-content: center;
    flex-wrap: wrap;
}

.hero-scroll {
    position: absolute;
    bottom: 1.5rem;
    left: 50%;
    transform: translateX(-50%);
    width: 22px;
    height: 36px;
    border: 1.5px solid var(--color-neutral-600);
    border-radius: 12px;
    opacity: 0.4;
}

.hero-scroll span {
    display: block;
    width: 3px;
    height: 8px;
    background: var(--color-neutral-600);
    border-radius: 2px;
    margin: 6px auto;
    animation: scroll-bob 1.6s ease-in-out infinite;
}

@keyframes scroll-bob {
    0%, 100% { transform: translateY(0); opacity: 0.5; }
    50%      { transform: translateY(8px); opacity: 1; }
}

@media (min-width: 768px) {
    .hero { padding: 7rem 0 6rem; }
    .hero-headline { font-size: var(--fs-hero); }
    .hero-subhead { font-size: 1.2rem; }
}

/* --------------------------------------------------------------------------
   Generic section
   -------------------------------------------------------------------------- */

.section {
    padding: 4.5rem 0;
}

@media (min-width: 768px) {
    .section { padding: 6rem 0; }
}

.section-eyebrow {
    text-transform: uppercase;
    letter-spacing: 0.08em;
    font-size: 0.8rem;
    font-weight: 600;
    color: var(--color-primary);
    margin-bottom: 0.75rem;
}

.section-title {
    font-size: 1.75rem;
    font-weight: 700;
    margin-bottom: 1rem;
    max-width: 720px;
}

.section-lede {
    color: var(--color-neutral-600);
    font-size: 1.05rem;
    max-width: 640px;
    margin-bottom: 2rem;
}

@media (min-width: 768px) {
    .section-title { font-size: 2rem; }
}

/* --------------------------------------------------------------------------
   Pillars
   -------------------------------------------------------------------------- */

.pillars {
    background-color: var(--color-neutral-100);
}

.pillar-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 1.5rem;
    margin-top: 2rem;
}

.pillar-card {
    background-color: var(--color-neutral-100);
    border: 1px solid var(--color-neutral-300);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    padding: 2rem 1.75rem;
    transition: transform 200ms ease, box-shadow 200ms ease;
}

.pillar-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
}

.pillar-card .pillar-icon {
    line-height: 1;
    margin-bottom: 0.85rem;
    display: block;
}

.pillar-card .pillar-icon svg {
    display: block;
}

.pillar-card h3 {
    color: var(--color-primary);
    font-size: 1.2rem;
    font-weight: 700;
    margin-bottom: 0.6rem;
}

.pillar-card p {
    color: var(--color-neutral-600);
    margin-bottom: 1rem;
}

.pillar-link {
    display: inline-flex;
    align-items: center;
    color: var(--color-primary);
    font-weight: 600;
    font-size: 0.95rem;
}

.pillar-link:hover { color: var(--color-primary-dark); }

/* --------------------------------------------------------------------------
   Audience
   -------------------------------------------------------------------------- */

.audience {
    background-color: var(--color-neutral-200);
}

.audience-list {
    display: grid;
    grid-template-columns: 1fr;
    gap: 0.85rem 2rem;
    margin-top: 2rem;
    color: var(--color-neutral-900);
    font-size: 1.05rem;
}

.audience-list li {
    display: flex;
    align-items: flex-start;
    gap: 0.75rem;
    line-height: 1.5;
}

.check {
    flex: 0 0 auto;
    color: var(--color-success);
    font-weight: 700;
    font-size: 1.15rem;
    line-height: 1.4;
}

@media (min-width: 720px) {
    .audience-list { grid-template-columns: 1fr 1fr; }
}

/* --------------------------------------------------------------------------
   Articles
   -------------------------------------------------------------------------- */

.articles { background-color: var(--color-neutral-100); }

.article-list {
    display: grid;
    gap: 1rem;
}

.article-card {
    display: grid;
    grid-template-columns: auto 1fr auto;
    gap: 1.25rem;
    align-items: center;
    background-color: var(--color-neutral-100);
    border: 1px solid var(--color-neutral-300);
    border-left: 4px solid var(--color-primary);
    border-radius: var(--radius);
    padding: 1.25rem 1.5rem;
    transition: transform 200ms ease, box-shadow 200ms ease;
}

.article-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow);
}

.article-badge {
    display: inline-block;
    background-color: var(--color-neutral-300);
    color: var(--color-neutral-600);
    font-size: 0.72rem;
    font-weight: 600;
    padding: 0.32rem 0.7rem;
    border-radius: 999px;
    cursor: default;
    white-space: nowrap;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    user-select: none;
}

.article-num {
    font-family: var(--font-family);
    font-weight: 700;
    color: var(--color-primary);
    font-size: 1.05rem;
    letter-spacing: 0.04em;
    width: 2.4rem;
    text-align: center;
}

.article-body h4 {
    font-size: 1.05rem;
    margin-bottom: 0.25rem;
    color: var(--color-neutral-900);
}

.article-body p {
    color: var(--color-neutral-600);
    margin: 0;
    font-size: 0.95rem;
}

.article-link {
    color: var(--color-primary);
    font-weight: 600;
    font-size: 0.95rem;
    white-space: nowrap;
}

@media (max-width: 600px) {
    .article-card {
        grid-template-columns: auto 1fr;
        grid-template-rows: auto auto;
    }
    .article-link,
    .article-badge { grid-column: 1 / -1; text-align: right; justify-self: end; }
}

/* --------------------------------------------------------------------------
   Open-source callout
   -------------------------------------------------------------------------- */

.callout {
    background-color: var(--color-primary);
    color: var(--color-neutral-100);
    padding: 4.5rem 0;
}

.callout-inner {
    max-width: 740px;
    text-align: center;
}

.callout h2 {
    color: var(--color-neutral-100);
    font-size: 2rem;
    margin-bottom: 1rem;
}

.callout p {
    color: rgba(255, 255, 255, 0.92);
    font-size: 1.05rem;
    margin-bottom: 1rem;
}

.callout-quote {
    font-style: italic;
    color: rgba(255, 255, 255, 0.85);
    border-left: 3px solid rgba(255, 255, 255, 0.4);
    padding-left: 1rem;
    text-align: left;
    margin: 1.5rem auto 2rem;
    max-width: 540px;
}

.callout-ctas {
    display: flex;
    gap: 0.85rem;
    justify-content: center;
    flex-wrap: wrap;
}

@media (min-width: 768px) {
    .callout { padding: 6rem 0; }
    .callout h2 { font-size: 2.4rem; }
}

/* --------------------------------------------------------------------------
   Footer
   -------------------------------------------------------------------------- */

.footer {
    background-color: var(--color-neutral-900);
    color: rgba(255, 255, 255, 0.78);
    padding: 3rem 0 2.5rem;
}

.footer-inner {
    display: grid;
    grid-template-columns: 1fr;
    gap: 2rem;
}

.footer-brand {
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}

.footer-logo {
    height: 30px;
    width: auto;
    color: var(--color-neutral-100);
    filter: brightness(0) invert(1);
}

.footer-tagline {
    color: rgba(255, 255, 255, 0.78);
    font-size: 0.95rem;
    margin: 0;
    max-width: 380px;
}

.footer-links {
    display: flex;
    flex-wrap: wrap;
    gap: 1.5rem;
}

.footer-links a {
    color: rgba(255, 255, 255, 0.92);
    font-size: 0.95rem;
    font-weight: 500;
}

.footer-links a:hover { color: var(--color-neutral-100); text-decoration: underline; }

.footer-meta {
    color: rgba(255, 255, 255, 0.55);
    font-size: 0.85rem;
    line-height: 1.7;
    margin: 0;
}

.footer-updated {
    color: rgba(255, 255, 255, 0.45);
    font-size: 0.78rem;
    margin: 0.6rem 0 0;
    letter-spacing: 0.02em;
}

@media (min-width: 768px) {
    .footer-inner {
        grid-template-columns: 1fr auto;
        align-items: start;
    }
    .footer-meta {
        grid-column: 1 / -1;
        padding-top: 1.5rem;
        border-top: 1px solid rgba(255, 255, 255, 0.08);
    }
}

/* --------------------------------------------------------------------------
   Stats strip — horizontal "by the numbers" between hero and pillars.
   -------------------------------------------------------------------------- */

.stats-strip {
    background-color: var(--color-neutral-200);
    border-top: 1px solid var(--color-neutral-300);
    border-bottom: 1px solid var(--color-neutral-300);
    padding: 2rem 0;
}

.stats-grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: 1.5rem;
    text-align: center;
}

.stat {
    padding: 0.5rem 1rem;
}

.stat-num {
    font-size: 2rem;
    font-weight: 700;
    color: var(--color-primary);
    line-height: 1.1;
    letter-spacing: -0.02em;
}

.stat-label {
    font-size: 0.78rem;
    color: var(--color-neutral-600);
    text-transform: uppercase;
    letter-spacing: 0.06em;
    font-weight: 600;
    margin-top: 0.4rem;
}

@media (min-width: 720px) {
    .stats-grid {
        grid-template-columns: repeat(4, 1fr);
        gap: 0;
    }
    .stat + .stat {
        border-left: 1px solid var(--color-neutral-300);
    }
}

@media (min-width: 768px) {
    .stat-num { font-size: 2.4rem; }
}

/* --------------------------------------------------------------------------
   Comparison block — "How this is different".
   -------------------------------------------------------------------------- */

.compare {
    background-color: var(--color-neutral-100);
}

.compare-grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: 1.25rem;
    margin-top: 2rem;
}

.compare-card {
    border: 1px solid var(--color-neutral-300);
    border-radius: var(--radius);
    padding: 1.75rem;
    background-color: var(--color-neutral-100);
    box-shadow: var(--shadow);
}

.compare-card.compare-other {
    border-top: 4px solid var(--color-danger);
}

.compare-card.compare-msmt {
    border-top: 4px solid var(--color-success);
}

.compare-card h3 {
    font-size: 1.05rem;
    color: var(--color-neutral-900);
    margin-top: 0;
    margin-bottom: 0.85rem;
}

.compare-list {
    display: flex;
    flex-direction: column;
    gap: 0.65rem;
}

.compare-list li {
    display: flex;
    align-items: flex-start;
    gap: 0.65rem;
    color: var(--color-neutral-900);
    font-size: 0.98rem;
    line-height: 1.45;
}

.compare-icon {
    flex: 0 0 auto;
    width: 1.1rem;
    height: 1.1rem;
    margin-top: 0.15rem;
    font-weight: 700;
    text-align: center;
    line-height: 1;
}

.compare-icon-x { color: var(--color-danger); }
.compare-icon-check { color: var(--color-success); }

@media (min-width: 720px) {
    .compare-grid { grid-template-columns: 1fr 1fr; gap: 1.5rem; }
}

/* --------------------------------------------------------------------------
   About-the-author card.
   -------------------------------------------------------------------------- */

.author {
    background-color: var(--color-neutral-200);
}

.author-card {
    background-color: var(--color-neutral-100);
    border: 1px solid var(--color-neutral-300);
    border-radius: var(--radius);
    padding: 2rem;
    margin-top: 2rem;
    max-width: 720px;
    box-shadow: var(--shadow);
}

.author-card h3 {
    font-size: 1.05rem;
    color: var(--color-primary);
    margin-top: 0;
    margin-bottom: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.author-card p {
    color: var(--color-neutral-900);
    font-size: 1.0rem;
    line-height: 1.65;
    margin-bottom: 1rem;
}

.author-links {
    display: flex;
    flex-wrap: wrap;
    gap: 1.25rem;
    font-size: 0.95rem;
}

.author-links a {
    color: var(--color-primary);
    font-weight: 600;
}

.author-links a:hover { color: var(--color-primary-dark); }

/* --------------------------------------------------------------------------
   Soften the bright-blue MIT callout into the dark-navy footer.
   -------------------------------------------------------------------------- */

.callout {
    position: relative;
}

.callout::after {
    content: '';
    position: absolute;
    left: 0;
    right: 0;
    bottom: 0;
    height: 24px;
    background: linear-gradient(
        to bottom,
        rgba(15, 48, 96, 0) 0%,
        var(--color-neutral-900) 100%
    );
    pointer-events: none;
}