:root {
    --primary: #4f46e5;
    --primary-hover: #4338ca;
    --bg: #f8fafc;
    --surface: #ffffff;
    --text-main: #0f172a;
    --text-muted: #64748b;
    --border: #e2e8f0;
    --card-shadow: 0 10px 30px rgba(0, 0, 0, 0.06);
}

* {
    box-sizing: border-box;
}
html {
    font-family: "Inter", system-ui, sans-serif;
    color: var(--text-main);
    background: var(--bg);
    margin: 0;
}

/* --- Shared header --- */
.site-header {
    padding: 20px 48px;
    border-bottom: 1px solid var(--border);
    background: var(--surface);
    display: flex;
    align-items: center;
    justify-content: space-between;
    position: sticky;
    top: 0;
    z-index: 10;
}
.site-logo {
    font-weight: 700;
    font-size: 1.25rem;
    text-decoration: none;
    color: var(--text-main);
}
.site-logo span {
    color: var(--primary);
}
.site-header__right {
    font-size: 0.8125rem;
    font-weight: 600;
    color: var(--text-muted);
}
.site-header__right a {
    color: var(--primary);
    text-decoration: none;
    margin-left: 0.5rem;
}
.site-nav {
    display: flex;
    align-items: center;
    gap: 1rem;
    flex-wrap: wrap;
    justify-content: flex-end;
}
.site-nav__link {
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--primary);
    text-decoration: none;
}
.site-nav__link:hover {
    text-decoration: underline;
}
.site-nav__text {
    font-size: 0.8125rem;
    color: var(--text-muted);
}
.site-nav__text[href] {
    color: var(--primary);
    text-decoration: none;
    font-weight: 600;
}
.site-nav__text[href]:hover {
    text-decoration: underline;
}
.site-nav__link--cta {
    padding: 0.5rem 1rem;
    border-radius: 0.65rem;
    background: var(--primary);
    color: #fff !important;
}
.site-nav__link--cta:hover {
    background: var(--primary-hover);
    text-decoration: none;
}

.site-main--landing {
    max-width: 52rem;
    width: 100%;
    padding-top: 2rem;
    padding-bottom: 4rem;
}
.site-hero--marketing h1 {
    font-size: 2.5rem;
    max-width: 40rem;
}
.site-hero__lead {
    font-size: 1.125rem;
    line-height: 1.65;
    color: var(--text-muted);
    margin: 0 0 1.75rem;
}
.landing-points {
    margin: 0 0 2rem;
    padding-left: 1.25rem;
    color: var(--text-main);
    line-height: 1.65;
    font-size: 1rem;
}
.landing-points li {
    margin-bottom: 0.75rem;
}
.landing-points li:last-child {
    margin-bottom: 0;
}
.landing-points strong {
    color: var(--text-main);
}
.home-cta {
    margin: 0;
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    gap: 1rem 1.5rem;
}
.landing-secondary-link {
    font-weight: 600;
    font-size: 0.9375rem;
    color: var(--primary);
    text-decoration: none;
}
.landing-secondary-link:hover {
    text-decoration: underline;
}

/* --- Home --- */
.site-main {
    max-width: 42rem;
    margin: 0 auto;
    padding: 48px 24px 64px;
}
.site-main--hub {
    max-width: 1100px;
    width: 100%;
    padding-top: 1rem;
}
.site-main--center {
    min-height: calc(100vh - 72px);
    display: flex;
    flex-direction: column;
    justify-content: center;
}
.site-hero {
    max-width: 42rem;
    margin-bottom: 2rem;
}
.btn-cta {
    display: inline-block;
    font-weight: 600;
    font-size: 1rem;
    padding: 0.9rem 1.5rem;
    border-radius: 0.75rem;
    background: var(--primary);
    color: #fff;
    text-decoration: none;
    box-shadow: var(--card-shadow);
    transition: background 0.2s, transform 0.2s;
}
.btn-cta:hover {
    background: var(--primary-hover);
    transform: translateY(-1px);
}
.site-hero__eyebrow {
    display: inline-block;
    font-size: 0.6875rem;
    font-weight: 700;
    letter-spacing: 0.08em;
    text-transform: uppercase;
    color: #7c3aed;
    background: #ede9fe;
    padding: 6px 12px;
    border-radius: 99px;
    margin-bottom: 1rem;
}
.site-hero h1 {
    font-size: 2.25rem;
    letter-spacing: -0.03em;
    line-height: 1.15;
    margin: 0 0 1rem;
}
.site-hero p {
    margin: 0;
    font-size: 1.0625rem;
    line-height: 1.6;
    color: var(--text-muted);
}
.site-hero .accent {
    color: var(--primary);
}

.challenge-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 1.5rem;
}
.home-err {
    color: #b91c1c;
    grid-column: 1 / -1;
}

.challenge-card {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 1.25rem;
    overflow: hidden;
    box-shadow: var(--card-shadow);
    transition: border-color 0.2s, box-shadow 0.2s;
}
.challenge-card:not(.challenge-card--soon):hover {
    border-color: #c4b5fd;
    box-shadow: 0 12px 40px rgba(79, 70, 229, 0.1);
}
.challenge-card--soon {
    opacity: 0.72;
}
.challenge-card__link {
    display: block;
    text-decoration: none;
    color: inherit;
    height: 100%;
}
.challenge-card__image-wrap {
    aspect-ratio: 16 / 9;
    background: linear-gradient(135deg, #e0e7ff, #f1f5f9);
    overflow: hidden;
}
.challenge-card__image {
    display: block;
    width: 100%;
    height: 100%;
    object-fit: cover;
}
.challenge-card__body {
    padding: 1.25rem 1.5rem 1.5rem;
}
.challenge-card__title {
    font-size: 1.2rem;
    font-weight: 700;
    margin: 0 0 0.5rem;
    letter-spacing: -0.02em;
}
.challenge-card__desc {
    font-size: 0.9375rem;
    line-height: 1.55;
    color: var(--text-muted);
    margin: 0 0 1.25rem;
}
.challenge-card__meta {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    gap: 0.5rem;
}
.chip {
    font-size: 0.75rem;
    font-weight: 600;
    padding: 0.35rem 0.65rem;
    border-radius: 99px;
    background: #f1f5f9;
    color: var(--text-main);
    border: 1px solid var(--border);
}
.chip--soon {
    color: var(--text-muted);
}

/* --- Captcha page --- */
.captcha-page {
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    margin: 0;
}
.captcha-main {
    flex: 1;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 2rem 1.5rem 3rem;
}
.captcha-card {
    width: 100%;
    max-width: 32rem;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 1.5rem;
    padding: 2rem;
    box-shadow: var(--card-shadow);
}
.captcha-card h1 {
    font-size: 1.5rem;
    margin: 0 0 0.5rem;
    letter-spacing: -0.02em;
}
.captcha-card p.lead {
    margin: 0 0 1.5rem;
    color: var(--text-muted);
    line-height: 1.5;
    font-size: 0.9375rem;
}
#captcha-track {
    height: 64px;
    background: #f1f5f9;
    border-radius: 99px;
    position: relative;
    overflow: hidden;
    border: 2px solid var(--border);
}
#captcha-target {
    width: 52px;
    height: 52px;
    background: var(--primary);
    border-radius: 50%;
    position: absolute;
    top: 4px;
    left: 4px;
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-weight: bold;
}
.captcha-card .btn-primary {
    width: 100%;
    margin-top: 1.5rem;
    background: var(--primary);
    color: white;
    padding: 14px 24px;
    border-radius: 0.75rem;
    border: none;
    font-weight: 600;
    font-size: 1rem;
    cursor: pointer;
    transition: background 0.2s, transform 0.2s;
}
.captcha-card .btn-primary:hover:not(:disabled) {
    background: var(--primary-hover);
    transform: translateY(-1px);
}
.captcha-card .btn-primary:disabled {
    opacity: 0.45;
    cursor: not-allowed;
}
#captcha-status {
    font-size: 0.8rem;
    color: #b91c1c;
    min-height: 1.2em;
    margin-top: 0.5rem;
}

.captcha-hint {
    font-size: 0.8rem;
    color: var(--text-muted);
    margin-bottom: 0.75rem;
    font-weight: 600;
}

@media (max-width: 600px) {
    .site-header {
        padding: 16px 20px;
    }
    .site-hero h1 {
        font-size: 1.75rem;
    }
}