:root {
    --arena-background: #07111f;
    --arena-surface: #101f30;
    --arena-border: #31526c;
    --arena-primary: #39a9ff;
    --arena-success: #39d98a;
    --arena-text: #f5f8fc;
    --arena-muted: #9bb1c5;
}

* {
    box-sizing: border-box;
}

html,
body {
    min-height: 100%;
}

body {
    margin: 0;

    background:
        radial-gradient(
            circle at top,
            #17334d 0,
            var(--arena-background) 55%
        );

    color: var(--arena-text);
    font-family:
        Inter,
        Arial,
        sans-serif;
}

button,
input,
select,
textarea {
    font: inherit;
}

a {
    color: inherit;
    text-decoration: none;
}

.technical-home {
    min-height: 100vh;

    display: grid;
    place-items: center;

    padding: 24px;
}

.technical-home__panel {
    width: min(100%, 620px);

    padding: 48px;

    background: rgba(16, 31, 48, 0.94);
    border: 2px solid var(--arena-border);
    border-radius: 18px;

    box-shadow:
        0 24px 70px rgba(0, 0, 0, 0.45);

    text-align: center;
}

.technical-home__status {
    display: inline-block;

    margin-bottom: 18px;
    padding: 8px 14px;

    color: var(--arena-success);
    background: rgba(57, 217, 138, 0.1);
    border: 1px solid rgba(57, 217, 138, 0.4);
    border-radius: 999px;

    font-size: 0.85rem;
    font-weight: 700;
    text-transform: uppercase;
}

.technical-home h1 {
    margin: 0 0 12px;

    color: var(--arena-primary);
    font-size: clamp(2.4rem, 7vw, 4rem);
}

.technical-home p {
    margin: 0;

    color: var(--arena-muted);
    font-size: 1.1rem;
    line-height: 1.7;
}

.technical-home__message {
    margin: 32px 0;
    padding: 18px;

    background: rgba(0, 0, 0, 0.2);
    border-left: 4px solid var(--arena-primary);
    border-radius: 8px;
}

.technical-home__button {
    display: inline-flex;
    align-items: center;
    justify-content: center;

    min-height: 48px;
    padding: 0 24px;

    background: var(--arena-primary);
    border-radius: 8px;

    color: #04101b;
    font-weight: 800;

    transition:
        transform 160ms ease,
        filter 160ms ease;
}

.technical-home__button:hover {
    transform: translateY(-2px);
    filter: brightness(1.12);
}

@media (max-width: 600px) {
    .technical-home {
        padding: 14px;
    }

    .technical-home__panel {
        padding: 32px 20px;
    }
}

.books-page,
.book-detail {
    width: min(1180px, calc(100% - 32px));
    margin: 0 auto;
    padding: 48px 0 80px;
}

.books-page__header {
    margin-bottom: 32px;
}

.books-page__eyebrow,
.book-detail__subject {
    color: var(--arena-primary);
    font-size: 0.85rem;
    font-weight: 800;
    letter-spacing: 0.1em;
    text-transform: uppercase;
}

.books-page__header h1,
.book-detail__information h1 {
    margin: 8px 0 10px;
}

.books-page__header p,
.book-detail__information p {
    color: var(--arena-muted);
    line-height: 1.6;
}

.book-grid {
    display: grid;
    grid-template-columns:
        repeat(auto-fill, minmax(240px, 1fr));
    gap: 24px;
}

.book-card {
    overflow: hidden;

    background: var(--arena-surface);
    border: 1px solid var(--arena-border);
    border-radius: 16px;

    transition:
        transform 160ms ease,
        border-color 160ms ease;
}

.book-card:hover {
    transform: translateY(-4px);
    border-color: var(--arena-primary);
}

.book-card__cover {
    aspect-ratio: 4 / 3;
    overflow: hidden;

    background: #0a1724;
}

.book-card__cover img,
.book-detail__cover img {
    width: 100%;
    height: 100%;
    object-fit: cover;
}

.book-card__placeholder {
    width: 100%;
    height: 100%;

    display: grid;
    place-items: center;

    font-size: 4rem;
}

.book-card__content {
    padding: 20px;
}

.book-card__subject {
    color: var(--arena-primary);
    font-size: 0.8rem;
    font-weight: 800;
    text-transform: uppercase;
}

.book-card h2 {
    margin: 8px 0;
}

.book-card p {
    color: var(--arena-muted);
    line-height: 1.5;
}

.book-card__action {
    display: inline-block;
    margin-top: 14px;

    color: var(--arena-success);
    font-weight: 800;
}

.book-detail__back {
    display: inline-block;
    margin-bottom: 24px;

    color: var(--arena-primary);
    font-weight: 700;
}

.book-detail__presentation {
    display: grid;
    grid-template-columns: 220px 1fr;
    gap: 32px;
    align-items: center;
}

.book-detail__cover {
    aspect-ratio: 3 / 4;
    overflow: hidden;

    background: var(--arena-surface);
    border: 1px solid var(--arena-border);
    border-radius: 14px;
}

.book-detail__metadata {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;

    margin-top: 20px;
}

.book-detail__metadata span {
    padding: 8px 12px;

    background: var(--arena-surface);
    border: 1px solid var(--arena-border);
    border-radius: 999px;

    color: var(--arena-muted);
}

.unit-list {
    display: grid;
    gap: 24px;

    margin-top: 48px;
}

.unit-card {
    padding: 28px;

    background: var(--arena-surface);
    border: 1px solid var(--arena-border);
    border-radius: 16px;
}

.unit-card__header > span {
    color: var(--arena-primary);
    font-weight: 800;
}

.unit-card__header h2 {
    margin: 6px 0 10px;
}

.unit-card__header p {
    color: var(--arena-muted);
    line-height: 1.6;
}

.chapter-list {
    display: grid;
    gap: 12px;

    margin-top: 24px;
}

.chapter-card {
    display: flex;
    justify-content: space-between;
    gap: 24px;

    padding: 18px;

    background: rgba(0, 0, 0, 0.18);
    border: 1px solid rgba(155, 177, 197, 0.2);
    border-radius: 12px;
}

.chapter-card__number {
    color: var(--arena-primary);
    font-size: 0.8rem;
    font-weight: 800;
    text-transform: uppercase;
}

.chapter-card h3 {
    margin: 5px 0;
}

.chapter-card p {
    margin: 0;

    color: var(--arena-muted);
    line-height: 1.5;
}

.chapter-card__information {
    min-width: 120px;

    display: flex;
    flex-direction: column;
    align-items: flex-end;
    gap: 8px;

    color: var(--arena-muted);
    font-size: 0.9rem;
}

.chapter-card__status {
    color: var(--arena-success);
    font-weight: 800;
}

.empty-state {
    padding: 48px;

    background: var(--arena-surface);
    border: 1px dashed var(--arena-border);
    border-radius: 16px;

    text-align: center;
}

@media (max-width: 700px) {
    .book-detail__presentation {
        grid-template-columns: 1fr;
    }

    .book-detail__cover {
        width: min(100%, 240px);
    }

    .chapter-card {
        flex-direction: column;
    }

    .chapter-card__information {
        align-items: flex-start;
    }
}

.mission-complete-alert {
    margin-bottom: 28px;
    padding: 20px;

    background:
        linear-gradient(
            135deg,
            rgba(38, 183, 107, 0.22),
            rgba(48, 129, 205, 0.18)
        );

    border: 2px solid var(--arena-success);
    border-radius: 14px;

    box-shadow:
        0 0 24px rgba(57, 217, 138, 0.16);
}

.mission-complete-alert strong {
    display: block;

    color: var(--arena-success);
    font-size: 1.2rem;
}

.mission-complete-alert span {
    display: block;

    margin-top: 5px;

    font-size: 1.05rem;
    font-weight: 800;
}

.mission-complete-alert p {
    color: var(--arena-muted);
}

.mission-complete-alert a {
    display: inline-flex;

    padding: 10px 16px;

    background: var(--arena-success);
    border-radius: 7px;

    color: #052116;
    font-weight: 900;
}