:root {
    --bg: #0b0d10;
    --card: #111418;
    --border: #1b1f24;
    --text-primary: #e9eef3;
    --text-secondary: #9ea9b2;
    --accent: #3fa9c9;
    --accent-soft: #5bbbd8;
    --radius: 6px;
    --max-width: 1180px;
    font-family: "Inter", sans-serif;
}

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

body {
    background: var(--bg);
    color: var(--text-primary);
    line-height: 1.55;
    overflow-x: hidden;
}

/* Header */
header {
    width: 100%;
    max-width: var(--max-width);
    margin: auto;
    height: 90px;
    padding: 0 24px;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.logo {
    display: flex;
    align-items: center;
    justify-content: center;
    height: 48px;
    width: 48px;
}

.logo img {
    width: 100%;
    height: 100%;
    object-fit: contain;
}

@media (max-width: 720px) {
    .logo {
        height: 40px;
        width: 40px;
    }
}

nav ul {
    display: flex;
    gap: 32px;
}

nav a {
    color: var(--text-secondary);
    text-decoration: none;
    font-size: 15px;
    transition: 0.2s;
}

nav a:hover {
    color: var(--accent);
}

/* Accent Button */
.btn-accent {
    padding: 10px 22px;
    border-radius: var(--radius);
    border: 1px solid var(--accent-soft);
    background: transparent;
    color: var(--accent);
    cursor: pointer;
    transition: 0.3s;
    font-size: 15px;
}

.btn-accent:hover {
    background: var(--accent);
    color: var(--bg);
}

/* Hero */
.hero {
    width: 100%;
    max-width: var(--max-width);
    padding: 100px 24px 40px;
    margin: auto;
}

.hero h1 {
    font-size: 56px;
    font-weight: 300;
    margin-bottom: 12px;
}

.subtitle {
    font-size: 18px;
    color: var(--text-secondary);
    margin-bottom: 48px;
}

.hero-media {
    display: grid;
    grid-template-columns: 2fr 1fr;
    gap: 32px;
}

.hero-img, 
.hero-img-right {
    width: 100%;
    height: 330px;
    border-radius: var(--radius);
    object-fit: cover;
    border: 1px solid var(--border);
}

/* Tile Section */
.tiles {
    width: 100%;
    max-width: var(--max-width);
    margin: auto;
    padding: 40px 24px 100px;
    display: grid;
    gap: 34px;
    grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
}

.tile {
    background: var(--card);
    padding-bottom: 14px;
    border: 1px solid var(--border);
    border-radius: var(--radius);
    transition: 0.3s;
}

.tile:hover {
    transform: scale(1.01);
}

.tile img {
    width: 100%;
    height: 170px;
    border-radius: var(--radius) var(--radius) 0 0;
    object-fit: cover;
    margin-bottom: 16px;
}

/* Tile Links */
.tile-link {
    display: block;
    text-decoration: none;
    color: inherit;
    border-radius: var(--radius);
    transition: transform 0.3s ease;
}

.tile-link:hover {
    transform: translateY(-5px);
}

/* タイル自体にカーソルポインターを追加 */
.tile {
    cursor: pointer;
}

/* タッチデバイス向けのフィードバック */
.tile-link:active .tile {
    transform: scale(0.98);
}
.tile h3 {
    margin: 0 16px;
    font-size: 20px;
    font-weight: 300;
    color: var(--accent);
}

.tile p {
    margin: 4px 16px 10px;
    color: var(--text-secondary);
    font-size: 15px;
}

/* Footer */
footer {
    text-align: center;
    padding-bottom: 50px;
    color: var(--text-secondary);
}

.socials {
    margin-bottom: 14px;
    display: flex;
    justify-content: center;
    gap: 22px;
}

.socials a {
    color: var(--accent);
    font-size: 16px;
    text-decoration: none;
}

.left-align {
    text-align: left;
}

/* 4. Floating Back to Top Button */
.back-to-top {
    position: fixed;
    bottom: 30px;
    right: 30px;
    width: 50px;
    height: 50px;
    background: var(--accent);
    color: #000;
    border-radius: 50%;
    text-decoration: none;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: bold;
    font-size: 24px;
    box-shadow: 0 4px 15px rgba(0,0,0,0.5);
    transition: transform 0.3s ease, background 0.3s;
    z-index: 100;
    opacity: 0.8;
}

.back-to-top:hover {
    transform: translateY(-5px);
    background: var(--text-primary);
    opacity: 1;
}