:root {
    --main-black: #1a1a1a;
    --main-green: #05728f;
    --accent-blue: #00b9be;
    --light-gray: #f4f4f4;
    --brand-text-opacity: rgba(0,0,0,0.02);
    --img-anim-duration: 6s;
}

body {
    margin: 0;
    font-family: "Helvetica Neue", Arial, "Hiragino Kaku Gothic ProN", "Hiragino Sans", sans-serif;
    color: var(--main-black);
    line-height: 1.6;
    overflow-x: hidden;
}

/* ヘッダー */
.main-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 10px 40px;
    border-bottom: 1px solid #eee;
    font-size: 12px;
    font-weight: bold;
    position: sticky;
    top: 0;
    background: #fff;
    z-index: 100;
}

.main-header ul {
    display: flex;
    list-style: none;
    gap: 20px;
}

.main-header a {
    text-decoration: none;
    color: #fff;
}

.btn-nav {
    background: var(--main-green);
    padding: 15px 40px;
    border-radius: 10px;
    font-size: 1rem;
}

.btn-nav:hover {
    opacity: .8;
}

.logo{
    max-width: 180px;
}

.logo img{
    width: 100%;
}

/* ヒーローエリア */
.hero {
    height: 90vh;
    display: flex;
    align-items: center;
    justify-content: center;
    text-align: center;
    position: relative;
    overflow: hidden;
    background: #fff;
}

.hero-content {
    z-index: 20;
    background-color: rgba(255,255,255,0.8);
    padding: 40px;
    border-radius: 20px;
}

.sub-copy {
    font-size: 1.2rem;
    letter-spacing: 0.1em;
    margin-bottom: 20px;
}

.hero h1 {
    font-size: 3.5rem;
    line-height: 1.2;
    margin-bottom: 30px;
}

.main-desc {
    font-size: 1.2rem;
    color: var(--main-green);
}

.main-desc strong span {
    font-size: 2rem;
    margin: 0 0 30px 0;
}

.brand-logo {
    max-width: 350px;
    margin: 0 auto;
}

.brand-logo img {
    width: 100%;
}

/* 画像グリッドアニメーション */
.image-grid .grid-item {
    position: absolute;
    width: 250px;
    height: 180px;
    background-size: cover;
    background-position: center;
    background-color: #ddd;
    z-index: 10;
    opacity: 0;
    border-radius: 8px;
    box-shadow: 0 4px 15px rgba(0,0,0,0.05);
    animation: randomFloat var(--img-anim-duration) ease-in-out infinite;
}

.img1 { top: 5%; left: 5%; animation-delay: 0s; }
.img2 { top: 8%; left: 40%; animation-delay: 1s; }
.img3 { top: 12%; right: 10%; animation-delay: 2s; }
.img4 { top: 35%; left: 15%; animation-delay: 0.5s; }
.img5 { top: 40%; right: 20%; animation-delay: 3s; }
.img6 { top: 60%; left: 8%; animation-delay: 1.5s; }
.img7 { top: 65%; left: 50%; animation-delay: 4s; }
.img8 { top: 70%; right: 5%; animation-delay: 2.5s; }
.img9 { bottom: 5%; left: 20%; animation-delay: 5s; }
.img10 { bottom: 8%; right: 15%; animation-delay: 3.5s; }
.img11 { bottom: 12%; left: 60%; animation-delay: 4.5s; }
.img12 { top: 15%; left: 75%; animation-delay: 6s; }

@keyframes randomFloat {
    0% { opacity: 0; transform: translateY(20px) scale(0.95); }
    10% { opacity: 0.8; transform: translateY(0px) scale(1); }
    80% { opacity: 0.8; transform: translateY(0px) scale(1); }
    100% { opacity: 0; transform: translateY(-20px) scale(0.95); }
}

/* ブランドセクション */
.brand-synchro-section {
    padding: 80px 0;
    background: #fff;
    overflow: hidden;
    position: relative;
    margin-top: 100px;
}

.brand-synchro-section::before {
    content: "KOUTOKUTEN";
    position: absolute;
    top: 20px;
    left: 5%;
    font-size: 15vw;
    font-weight: 900;
    color: rgba(0,0,0,0.03);
    line-height: 1;
    white-space: nowrap;
    z-index: 1;
}

.brand-container {
    max-width: 1280px;
    margin: 0 auto;
    padding: 0 20px;
    position: relative;
    z-index: 2;
}

.black-box-content {
    display: inline-flex;
    flex-direction: column;
    align-items: flex-start;
    gap: 15px;
    margin-bottom: 20px;
}

.black-box-content .tag, .black-box-content .main-label {
    background: var(--main-green);
    color: #fff;
    padding: 10px 20px;
    font-size: 2rem;
    border-radius: 10px;
}

.tire-running-img {
    width: 100%;
    margin-top: 40px;
}

.tire-running-img video {
    width: 100%;
}

/* ポイントセクション */
.point-section {
    padding: 100px 0;
    background: var(--light-gray);
    position: relative;
    overflow: hidden;
}

.point-bg-text {
    position: absolute;
    top: -20px;
    right: 5%;
    font-size: 15vw;
    font-weight: 900;
    color: rgba(0,0,0,0.03);
    line-height: 1;
}

.container {
    max-width: 1280px;
    margin: 0 auto;
    padding: 0 20px;
    position: relative;
}

.section-title span {
    background: var(--main-green);
    color: #fff;
    padding: 5px 15px;
    display: inline-block;
    font-size: 2rem;
    font-weight: normal;
    border-radius: 10px;
}

.lead-text{
    font-size: 1.2rem;
    margin-top: 50px;
}

.card-wrapper {
    display: flex;
    gap: 20px;
    margin-top: 50px;
}

.card { flex: 1; }

.card-img {
    height: 400px;
    background-size: cover;
    position: relative;
    display: flex;
    align-items: flex-end;
}

.card-tag {
    background: rgba(0,0,0,0.7);
    color: #fff;
    padding: 10px;
    margin: 15px;
    font-size: 1.8rem;
    border-bottom: 3px solid var(--accent-blue);
}

/* CTA */
.cta-section {
    text-align: center;
    padding: 100px 0;
}

.cta-text{
    font-size: 1.6rem;
}

.btn-main {
    display: inline-block;
    padding: 20px 60px;
    background: var(--main-green);
    color: #fff;
    text-decoration: none;
    font-weight: bold;
    font-size: 1.2rem;
    border-radius: 10px;
    transition: 0.3s;
}

.btn-main:hover {
    opacity: .8;
}

/* =========================================================================
   追加：フッターのデザイン
   ========================================================================= */
.main-footer {
    background: #212529;
    color: #fff;
    padding: 60px 0 20px;
    text-align: center;
}

.footer-container {
    max-width: 1280px;
    margin: 0 auto;
    padding: 0 20px;
}

.footer-logo {
    max-width: 180px;
    margin: 0 auto 30px;
}

.footer-logo img { width: 100%; }

.footer-links {
    list-style: none;
    padding: 0;
    display: flex;
    justify-content: center;
    gap: 30px;
    margin-bottom: 40px;
}

.footer-links a {
    color: #ccc;
    text-decoration: none;
    font-size: 0.9rem;
    transition: 0.3s;
}

.footer-links a:hover { color: #fff; }

.copyright {
    font-size: 0.8rem;
    color: #666;
    border-top: 1px solid #333;
    padding-top: 20px;
}

/* =========================================================================
   追加：スクロールフェードインアニメーション
   ========================================================================= */
.scroll-reveal {
    opacity: 0;
    transform: translateY(30px);
    transition: opacity 1.2s ease, transform 1.2s ease;
}

.scroll-reveal.active {
    opacity: 1;
    transform: translateY(0);
}

/* カードなど、連続する要素に少し遅延をかける場合 */
.card-wrapper .card:nth-child(2) {
    transition-delay: 0.2s;
}


/* =========================================================================
   レスポンシブ対応 (Media Queries)
   ========================================================================= */

.only-sp{
    display: none;
}

/* タブレットサイズ以下 (max-width: 1024px) */
@media screen and (max-width: 1024px) {
    .image-grid .grid-item {
        width: 180px; /* 画像を少し小さく */
        height: 130px;
    }
}

/* スマートフォンサイズ (max-width: 768px) */
@media screen and (max-width: 768px) {
    /* ヘッダー */
    .main-header {
        padding: 10px 20px;
    }
    .logo {
        max-width: 140px;
    }
    .btn-nav {
        padding: 12px 15px;
        font-size: 0.9rem;
    }

    /* ヒーローエリア */
    .hero {
        height: auto;
        padding: 100px 0;
    }
    .hero-content {
        width: 90%;
        padding: 30px 20px;
    }
    .sub-copy {
        font-size: 1rem;
    }
    .main-desc {
        font-size: 1rem;
    }
    /* スマホでは浮遊画像を減らすか、重なりを避けるために非表示にするのも手です */
    .image-grid .grid-item {
        width: 120px;
        height: 90px;
    }

    /* ブランドセクション */
    .brand-synchro-section {
        margin-top: 50px;
        padding: 60px 0;
    }
    .brand-synchro-section::before,
    .point-bg-text {
        font-size: 20vw; /* 背景文字を少し強調 */
        top: 0;
    }
    .black-box-content .tag, 
    .black-box-content .main-label {
        font-size: 1.2rem; /* 文字サイズをスマホ向けに */
        width: 100%;
        box-sizing: border-box;
    }

    /* ポイントセクション（カードの縦並び化） */
    .card-wrapper {
        flex-direction: column; /* 横から縦へ */
        gap: 30px;
    }
    .card-img {
        height: 300px;
    }
    .section-title span {
        font-size: 1.3rem;
        line-height: 1.4;
    }
    .card-tag {
        font-size: 1.2rem;
    }

    /* CTA */
    .cta-section {
        padding: 60px 20px;
    }
    .cta-text {
        font-size: 1.2rem;
    }
    .btn-main {
        width: 100%;
        padding: 20px 0;
        box-sizing: border-box;
    }

    /* フッター */
    .footer-links {
        flex-direction: column;
        gap: 15px;
    }

    .only-sp{
        display: block;
    }
}

/* 小さなスマホ向け (max-width: 480px) */
@media screen and (max-width: 480px) {
    .hero h1 {
        font-size: 1.8rem;
    }
}