html {
    font-family: 'Poppins', 'Noto Sans JP', sans-serif;
    font-weight: 400;
    color: #1a1a1a;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

body {
    min-height: 100vh;
    background-color: #fff;
    line-height: 1.75;
}

/* ===== Headings ===== */
h1, h2, h3, h4, h5 {
    font-weight: 700;
    letter-spacing: 0.03em;
    color: #0b132b;
    text-rendering: optimizeLegibility;
}

h1 {
    font-size: 2.5rem;
}

h2 {
    font-size: 1.875rem;
}

h3 {
    font-size: 1.375rem;
}

/* ===== Lead Text ===== */
.lead {
    font-weight: 400;
    line-height: 1.9;
    color: #f8f9fa;
    letter-spacing: 0.01em;
}

/* ===== Buttons ===== */
.btn-light {
    color: #003f6f;
    border: none;
    border-radius: 0.5rem;
    font-weight: 600;
    transition: all 0.3s ease-in-out;
}

    .btn-light:hover {
        background-color: #eaf3fa;
        transform: translateY(-1px);
    }

/* ===== Hero Section ===== */
.hero {
    text-shadow: 0 2px 8px rgba(0, 0, 0, 0.25);
}

/* ===== Sidebar ===== */
.sidebar {
    flex-shrink: 0;
    width: 250px;
    background-color: #f8f9fa;
}

    .sidebar .nav-link.active {
        background-color: #e9ecef;
        color: #212529;
        font-weight: 600;
    }

/* ===== Main Content ===== */
.main-content {
    flex-grow: 1;
    padding: 1.5rem;
    margin-left: 0; /* default for mobile */
}

/* ===== Nav Links ===== */
.nav-link {
    color: #495057;
    border-radius: 0.375rem;
    transition: background-color 0.2s ease-in-out;
}

    .nav-link:hover {
        background-color: #f1f3f5;
    }

/* ===== Mobile (≤ 768px) ===== */
@media (max-width: 768px) {
    .sidebar {
        position: absolute;
        top: 0;
        left: -250px;
        height: 100%;
        transition: left 0.3s ease-in-out;
        z-index: 1000;
    }

        .sidebar.show {
            left: 0;
        }

    h1 {
        font-size: 2rem;
    }

    .lead {
        font-size: 1rem;
    }
}