*,
*::before,
*::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

:root {
    --col-gold: #c9a84c;
    --col-oxford-blue: #001128;
}

body {
    background: #fff;
}

.wrapper {
    font-family: "Noto Serif JP", serif;
    min-width: 900px;
}

#corp-page img.full {
    width: 100%;
    display: block;
}

.banner-row {
    display: grid;
    grid-template-columns: 1fr 1fr 1fr 1fr;
    width: 100%;
    grid-auto-rows: calc(100vw / 4 / 3);
}

.banner-row img {
    width: 100%;
    height: 100%;
    display: block;
    object-fit: cover;
    object-position: center;
}

.challenge-btn {
    cursor: pointer;
    transition: opacity 0.15s;
}

.challenge-btn:hover {
    opacity: 0.85;
}

/* ===== リセット・ベース ===== */
*,
*::before,
*::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html,
body {
    font-size: 10px;
}

html {
    scroll-behavior: smooth;
}

body {
    /*font-family: 'Hiragino Mincho ProN', 'Yu Mincho', 'MS Mincho', Georgia, serif;*/
    background: var(--col-oxford-blue);
    color: #e8e4d9;
    line-height: 1.9;
    font-size: 16px;
}

/* ===== ヘッダー ===== */
header {
    background: var(--col-oxford-blue);
    border-bottom: 3px solid var(--col-gold);
    padding: 0;
    position: sticky;
    top: 0;
    z-index: 100;
}

.main-hdr-ttl {
    color: #ffffff;
    font-size: 2.5rem;
    font-weight: bold;
    letter-spacing: 2px;
    margin: 0 auto;
    max-width: 900px;
    padding: 18px 32px;
}



/* ===== 数式背景装飾 ===== */
.formula-bg {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    pointer-events: none;
    z-index: 0;
    overflow: hidden;
    opacity: 0.07;
    /*font-family: 'Courier New', monospace;*/
    font-size: 13px;
    color: var(--col-gold);
    white-space: nowrap;
    line-height: 2.2;
    padding: 20px;
    word-break: break-all;
}

/* ===== メインコンテンツ ===== */
main {
    position: relative;
    z-index: 1;
    max-width: 900px;
    margin: 0 auto;
    padding: 56px 32px 120px;
}

/* ===== セクション共通 ===== */
.section {
    margin-bottom: 60px;
}

.section-tag {
    background: var(--col-gold);
    color: var(--col-oxford-blue);
    font-size: 1.6rem;
    font-weight: bold;
    letter-spacing: .36em;
    margin-bottom: 2em;
    padding: .36em 1.27em;
    width: fit-content;
}

/* ===== 問題エリア ===== */
.problem-box {
    background: #051a40;
    border-left: .4em solid var(--col-gold);
    border-radius: .2em;
    font-size: 1rem;
    padding: 3.6em 4em;
    margin-top: .8em;
}

.problem-ttl {
    color: var(--col-gold);
    font-size: 2.7rem;
    font-weight: bold;
    letter-spacing: .18em;
    margin-bottom: 1.1em;
}

.problem-intro {
    color: #ddd;
    font-size: 2.2rem;
    margin-bottom: 1.4em;
}

.problem-item {
    border-top: 1px solid #0d3060;
    color: #e0dcce;
    font-size: 2.1rem;
    padding: 1em 0;
}

.problem-item:last-child {
    border-bottom: 1px solid #0d3060;
}

.problem-num {
    color: var(--col-gold);
    font-weight: bold;
    margin-right: .5em;
}

/* ===== 解答エリア ===== */
.answer-section {
    margin-bottom: 48px;
}

.answer-header {
    align-items: center;
    border-bottom: 1px solid #1a3a6a;
    display: flex;
    font-size: 2.3rem;
    gap: .9em;
    margin-bottom: 1.26em;
    padding-bottom: .52em;
}

.answer-num {
    align-items: center;
    background: #8B0000;
    border-radius: 50%;
    color: #fff;
    display: flex;
    flex-shrink: 0;
    /*font-family: sans-serif;*/
    font-size: .82em;
    font-weight: bold;
    height: 2.15em;
    justify-content: center;
    width: 2.15em;
}

.answer-title {
    color: #fff;
    letter-spacing: .01em;
}

.answer-verdict {
    background: #0d3060;
    border: 1px solid var(--col-gold);
    border-radius: .13em;
    color: var(--col-gold);
    font-size: 2rem;
    font-weight: bold;
    padding: .4em 1.33em;
    margin-bottom: 1.33em;
    letter-spacing: .13em;
    width: fit-content;
}

/* ===== テキスト本文 ===== */
.body-text {
    color: #d8d4c8;
    font-size: 2.1rem;
    line-height: 2.0;
    margin-bottom: 1em;
}

.body-text.indent {
    margin-left: 1.5em;
}

/* ===== 数式ブロック ===== */
.math-block {
    background: #051a40;
    border-left: .2em solid #1a3a6a;
    border-radius: .1em;
    font-size: 2rem;
    margin: 1.2em 0;
    overflow-x: auto;
    padding: 1.2em 1.4em;
}

.math-block .katex-display {
    margin: 1em 0;
}

/* ===== ポイントボックス ===== */
.point-box {
    background: #0a2a50;
    border: .1em solid var(--col-gold);
    border-radius: .1em;
    border-top: .15em solid var(--col-gold);
    font-size: 2rem;
    margin: 1.4em 0;
    padding: 1.2em 1.6em;
}

.point-box .point-label {
    color: var(--col-gold);
    font-size: 1.7rem;
    /*font-family: sans-serif;*/
    font-weight: bold;
    letter-spacing: .42em;
    margin-bottom: .93em;
}

.point-box p {
    color: #c8c4b8;
    line-height: 1.9;
    margin-bottom: .67em;
}

.point-box p:last-child {
    margin-bottom: 0;
}

/* ===== ケース分類 ===== */
.case-block {
    background: #041530;
    border-left: .4em solid #8B0000;
    font-size: 1rem;
    padding: 1.6em 2.4em;
    margin: 3em 0;
    border-radius: .2em;
}

.case-label {
    color: #f66;
    /*font-family: sans-serif;*/
    font-size: 1.8rem;
    font-weight: bold;
    letter-spacing: .15em;
    margin-bottom: .67em;
}

.case-result-ng {
    display: inline-block;
    color: #f44;
    font-size: 1.8rem;
    /*font-family: sans-serif;*/
    letter-spacing: .07em;
    margin-top: .62em;
}

.case-result-ok {
    display: inline-block;
    color: #4d8;
    font-size: 1.8rem;
    /*font-family: sans-serif;*/
    letter-spacing: .07em;
    margin-top: .62em;
}

/* ===== 区切り線 ===== */
.divider {
    border: none;
    border-top: 1px solid #1a3a6a;
    margin: 60px 0;
}

/* ===== 結論 ===== */
.conclusion {
    background: #051a40;
    border: 1px solid var(--col-gold);
    border-radius: 2px;
    font-size: 1.9rem;
    margin: 2.85em auto 0;
    padding: 2.28em;
    text-align: center;
}

.conclusion p {
    color: var(--col-gold);
    letter-spacing: .21em;
    /*font-family: sans-serif;*/
}

/* ===== 固定リクルートバナー（右下） ===== */
/* 閉じるボタン */

.recruit-fixed {
    position: fixed;
    bottom: 28px;
    display: block;
    right: 28px;
    width: 300px;
    z-index: 200;
    cursor: pointer;
    transition: opacity .3s, visibility .3s, transform .2s;
    box-shadow: 0 8px 32px rgba(0, 0, 0, 0.6);
    border-radius: 4px;
    opacity: 1;
    overflow: hidden;
    visibility: visible;
}

.recruit-fixed:hover {
    opacity: 0.9;
    transform: translateY(-3px);
}

.recruit-fixed img {
    width: 100%;
    display: block;
}

.recruit-fixed .close-btn {
    position: absolute;
    top: 6px;
    right: 6px;
    width: 24px;
    height: 24px;
    background: rgba(0, 0, 0, 0.55);
    color: #fff;
    font-size: 14px;
    line-height: 24px;
    text-align: center;
    border-radius: 50%;
    cursor: pointer;
    /*font-family: sans-serif;*/
    z-index: 10;
}

.recruit-fixed .close-btn:hover {
    background: rgba(0, 0, 0, 0.85);
}

.recruit-fixed.is-hidden {
    opacity: 0;
    visibility: hidden;
    pointer-events: none;
}

.to-recruit {
    width: 100%;
}

.to-recruit-a {
    display: block;
    margin: 0 auto;
    width: clamp(900px, 100%, 1200px);
}

.to-recruit-img {
    width: 100%;
}

.main-ftr {
    border-top: 2px solid var(--col-gold);
    padding: 10px;
}

.main-ftr-copyright {
    font-size: 14px;
    text-align: center;
}

@media screen and (min-width: 1920px) {

    .main-hdr-ttl,
    .main-ctr {
        margin-left: 510px;
    }

    .to-recruit-a {
        margin-left: 360px;
    }

    #recruit-fixed {
        right: calc(28px + 100vw - 1920px);
    }
}