/* --- 基本設定 & 変数 --- */
:root {
    --primary-color: #3498db;
    --secondary-color: #2c3e50;
    --background-color: #f4f6f9;
    --text-color: #333;
    --white-color: #fff;
    --base-font-size: 16px;
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    line-height: 1.6;
    background-color: var(--background-color);
    color: var(--text-color);
    font-size: var(--base-font-size);
}

/* --- ヘッダー --- */
.header {
    background-color: var(--white-color);
    box-shadow: 0 2px 5px rgba(0,0,0,0.1);
    padding: 1rem 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    position: sticky;
    top: 0;
    z-index: 100;
}

.logo {
    font-size: 1.5rem;
    font-weight: bold;
    color: var(--primary-color);
    text-decoration: none;
}

.nav-list {
    list-style: none;
    display: flex;
    gap: 1.5rem;
}

.nav-list a {
    text-decoration: none;
    color: var(--secondary-color);
    font-weight: 500;
    transition: color 0.3s ease;
}

.nav-list a:hover {
    color: var(--primary-color);
}

.hamburger-menu {
    display: none; /* デスクトップでは非表示 */
    background: none;
    border: none;
    cursor: pointer;
    flex-direction: column;
    gap: 5px;
}

.hamburger-menu span {
    display: block;
    width: 25px;
    height: 3px;
    background-color: var(--secondary-color);
}

/* --- ヒーローセクション --- */
.hero {
    background: linear-gradient(rgba(0, 0, 0, 0.5), rgba(0, 0, 0, 0.5)), url('https://source.unsplash.com/random/1600x900/?technology,abstract') no-repeat center center/cover;
    color: var(--white-color);
    text-align: center;
    padding: 6rem 1rem;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 60vh;
}


[Image of an abstract technology background]


.hero-content h1 {
    font-size: 3rem;
    margin-bottom: 1rem;
}

.hero-content p {
    font-size: 1.2rem;
    margin-bottom: 2rem;
}

.cta-button {
    background-color: var(--primary-color);
    color: var(--white-color);
    padding: 0.8rem 2rem;
    border-radius: 5px;
    text-decoration: none;
    font-weight: bold;
    transition: background-color 0.3s ease;
}

.cta-button:hover {
    background-color: #2980b9;
}

/* --- 特徴セクション --- */
.features {
    padding: 4rem 2rem;
    text-align: center;
}

.section-title {
    font-size: 2.5rem;
    margin-bottom: 3rem;
    color: var(--secondary-color);
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 2rem;
    max-width: 1200px;
    margin: 0 auto;
}

.feature-card {
    background-color: var(--white-color);
    padding: 2rem;
    border-radius: 8px;
    box-shadow: 0 4px 15px rgba(0,0,0,0.08);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.feature-card:hover {
    transform: translateY(-10px);
    box-shadow: 0 8px 25px rgba(0,0,0,0.12);
}

.feature-card .icon {
    font-size: 3rem;
    margin-bottom: 1rem;
}

.feature-card h3 {
    font-size: 1.5rem;
    margin-bottom: 0.5rem;
    color: var(--secondary-color);
}

/* --- フッター --- */
.footer {
    background-color: var(--secondary-color);
    color: var(--white-color);
    text-align: center;
    padding: 1.5rem;
}

/* --- アニメーション --- */
.fade-in {
    opacity: 0;
    transform: translateY(20px);
    transition: opacity 0.6s ease-out, transform 0.6s ease-out;
}

.fade-in.visible {
    opacity: 1;
    transform: translateY(0);
}


/* --- レスポンシブ対応 (モバイル) --- */
@media (max-width: 768px) {
    .nav {
        /* JSでactiveクラスを付与して表示 */
        display: none;
        position: absolute;
        top: 100%;
        left: 0;
        width: 100%;
        background-color: var(--white-color);
    }
    
    .nav.active {
        display: block;
    }

    .nav-list {
        flex-direction: column;
        align-items: center;
        padding: 1rem 0;
    }

    .hamburger-menu {
        display: flex;
    }

    .hero-content h1 {
        font-size: 2.2rem;
    }
}