body {
    font-family: 'Segoe UI', Arial, sans-serif;
    line-height: 1.7;
    background-color: #f4f8fa;
    color: #222e36;
    margin: 0;
    padding: 0;
    min-height: 100vh;
    
    scrollbar-width: thin;
    scrollbar-color: #bcd7ec #f4f8fa;
}

.container {
    max-width: 860px;
    margin: 2rem auto;
    padding: 2rem;
    background: #fff;
    box-shadow: 0 4px 32px rgba(44,62,80,0.12);
    border-radius: 20px;
}

.header {
    text-align: center;
    margin-bottom: 32px;
}

.cover-image {
    width: 100%;
    height: auto;
    margin: 28px 0 10px 0;
    border-radius: 20px;
    box-shadow: 0 2px 12px rgba(44,62,80,0.09);
}

h1 {
    font-size: 2.35em;
    color: #223040;
    margin-bottom: 0.8em;
    letter-spacing: -0.01em;
    line-height: 1.2;
    font-weight: 700;
}

h2 {
    font-size: 1.5em;
    color: #294363;
    margin: 1.9em 0 0.75em 0;
    font-weight: 600;
    line-height: 1.3;
}

h3, h4 {
    color: #3e5d7b;
    margin-top: 1.5em;
    margin-bottom: 0.7em;
    font-weight: 600;
}

p, li {
    font-size: 1.08em;
    margin-bottom: 1em;
}

ul, ol {
    padding-left: 24px;
    margin-bottom: 1.6em;
}

li {
    margin-bottom: 0.6em;
}

section {
    margin-bottom: 56px;
}

section img {
    width: 100%;
    max-width: 720px;
    display: block;
    margin: 24px auto 0 auto;
    height: auto;
    border-radius: 14px;
    box-shadow: 0 2px 10px rgba(44,62,80,0.08);
}

footer {
    text-align: center;
    font-size: 1.15em;
    margin-top: 48px;
    padding: 28px 10px 12px 10px;
    border-top: 1.5px solid #e3eaf0;
    color: #36495f;
    background: #f7fafc;
    border-radius: 0 0 16px 16px;
    box-shadow: 0 -1px 6px rgba(44,62,80,0.06);
}

.sources ul {
    list-style-type: disc;
}

.challenge {
    margin-top: 1.8em;
    font-size: 1.06em;
    color: #5b7590;
    background: #eaf5ff;
    border-radius: 10px;
    padding: 16px 10px;
    box-shadow: 0 1px 5px rgba(44,62,80,0.04);
    font-style: italic;
}

/* Стили для подстрочных ссылок */
sup {
    font-size: 0.92em;
    color: #558dd2;
}

/* Ссылки (если появятся) */
a {
    color: #3184c6;
    text-decoration: underline;
    transition: color 0.18s;
}
a:hover, a:focus {
    color: #29577c;
}

a:focus-visible {
    outline: 2px dashed #3184c6;
    outline-offset: 2px;
}

/* Адаптивность */
@media (max-width: 990px) {
    .container {
        max-width: 96vw;
        padding: 18px 2vw 36px 2vw;
    }
    section img, .cover-image {
        max-width: 100%;
    }
}

@media (max-width: 600px) {
    .container {
        padding: 8vw 3vw 10vw 3vw;
        margin: 10px 0 16px 0;
        border-radius: 10px;
    }
    h1 {
        font-size: 1.25em;
    }
    h2 {
        font-size: 1.05em;
    }
    h3, h4 {
        font-size: 0.96em;
    }
    section img, .cover-image {
        border-radius: 10px;
        box-shadow: 0 1px 6px rgba(44,62,80,0.05);
        margin: 12px auto 0 auto;
    }
    p, li {
        font-size: 1em;
    }
    footer {
        font-size: 1em;
        border-radius: 0 0 10px 10px;
        padding: 20px 2vw 10px 2vw;
    }
    .challenge {
        font-size: 0.99em;
        padding: 12px 7px;
    }
}

/* Мелкая доработка для читаемости списков */
ol li, ul li {
    line-height: 1.65;
}

/* Красивый скролл на мобильных и десктопе */

body::-webkit-scrollbar {
    width: 8px;
    background: #f4f8fa;
}
body::-webkit-scrollbar-thumb {
    background: #bcd7ec;
    border-radius: 8px;
}