:root {
    --primary-bg: #0f172a;
    --secondary-bg: #1e293b;
    --accent-color: #38bdf8;
    --accent-glow: rgba(56, 189, 248, 0.5);
    --text-main: #f8fafc;
    --text-secondary: #94a3b8;
    --glass-bg: rgba(255, 255, 255, 0.03);
    --border-color: rgba(255, 255, 255, 0.1);
}

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

body {
    font-family: 'Inter', sans-serif;
    background-color: var(--primary-bg);
    color: var(--text-main);
    line-height: 1.6;
    overflow-x: hidden;
}

.background-mesh {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: -1;
    background-image:
        radial-gradient(at 0% 0%, rgba(56, 189, 248, 0.15) 0px, transparent 50%),
        radial-gradient(at 100% 100%, rgba(129, 140, 248, 0.15) 0px, transparent 50%);
}

.container {
    max-width: 1100px;
    margin: 0 auto;
    padding: 0 40px;
}

nav {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 30px 0;
}

.logo {
    display: flex;
    align-items: center;
    gap: 12px;
    font-weight: 800;
    font-size: 1.5rem;
    letter-spacing: -0.5px;
}

.logo-img {
    width: 40px;
    height: 40px;
    border-radius: 8px;
}

.hero {
    padding: 100px 0 80px;
    text-align: center;
}

.hero h1 {
    font-size: 4rem;
    font-weight: 800;
    line-height: 1.1;
    margin-bottom: 24px;
    letter-spacing: -2px;
}

.highlight {
    background: linear-gradient(to right, #38bdf8, #818cf8);
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
}

.hero p {
    font-size: 1.25rem;
    color: var(--text-secondary);
    max-width: 700px;
    margin: 0 auto 40px;
}

.btn {
    display: inline-block;
    padding: 16px 32px;
    border-radius: 12px;
    font-weight: 600;
    text-decoration: none;
    transition: all 0.3s ease;
}

.btn-primary {
    background-color: var(--accent-color);
    color: var(--primary-bg);
    box-shadow: 0 10px 20px -5px var(--accent-glow);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 15px 25px -5px var(--accent-glow);
    background-color: #7dd3fc;
}

.features {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 30px;
    padding-bottom: 100px;
}

.feature-card {
    background: var(--glass-bg);
    border: 1px solid var(--border-color);
    padding: 40px;
    border-radius: 24px;
    backdrop-filter: blur(10px);
    transition: all 0.3s ease;
}

.feature-card:hover {
    border-color: var(--accent-color);
    transform: translateY(-5px);
    background: rgba(255, 255, 255, 0.05);
}

.icon-box {
    font-size: 2.5rem;
    margin-bottom: 20px;
}

.feature-card h3 {
    font-size: 1.5rem;
    margin-bottom: 15px;
}

.feature-card p {
    color: var(--text-secondary);
    font-size: 1rem;
}

.how-to-use {
    text-align: center;
    padding: 100px 0;
    border-top: 1px solid var(--border-color);
}

.how-to-use h2 {
    font-size: 2.5rem;
    margin-bottom: 60px;
}

.steps {
    display: flex;
    justify-content: center;
    gap: 40px;
    flex-wrap: wrap;
}

.step {
    flex: 1;
    min-width: 200px;
    max-width: 250px;
}

.step-num {
    display: inline-flex;
    width: 50px;
    height: 50px;
    background: var(--secondary-bg);
    border: 2px solid var(--accent-color);
    border-radius: 50%;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
    font-weight: 800;
    margin-bottom: 20px;
}

.design-preview {
    padding: 100px 0;
    text-align: center;
    background: radial-gradient(circle at center, rgba(56, 189, 248, 0.05) 0%, transparent 70%);
}

.preview-content h2 {
    font-size: 2.5rem;
    margin-bottom: 24px;
}

.preview-content p {
    color: var(--text-secondary);
    font-size: 1.1rem;
    max-width: 800px;
    margin: 0 auto;
}

footer {
    padding: 80px 0;
    text-align: center;
    border-top: 1px solid var(--border-color);
}

.footer-bottom {
    color: var(--text-secondary);
    font-size: 0.9rem;
}

@media (max-width: 768px) {
    .hero h1 {
        font-size: 2.5rem;
    }

    .hero p {
        font-size: 1.1rem;
    }

    .container {
        padding: 0 24px;
    }

    .preview-content h2 {
        font-size: 2rem;
    }
}

/* Language Switching */
body.lang-en [lang="ja"] {
    display: none !important;
}

body.lang-ja [lang="en"] {
    display: none !important;
}

/* Navigation Updates */
nav {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 30px 0;
}

.nav-left {
    display: flex;
    align-items: center;
    gap: 20px;
}

.back-home {
    color: var(--text-main);
    text-decoration: none;
    font-size: 0.9em;
    opacity: 0.7;
    transition: opacity 0.2s;
    font-weight: 600;
}

.back-home:hover {
    opacity: 1;
    color: var(--accent-color);
}

.lang-switch {
    display: flex;
    gap: 10px;
}

.lang-btn {
    background: transparent;
    border: 1px solid var(--border-color);
    color: var(--text-secondary);
    padding: 6px 12px;
    cursor: pointer;
    border-radius: 6px;
    font-size: 0.9em;
    font-weight: 600;
    transition: all 0.2s;
}

.lang-btn:hover {
    border-color: var(--accent-color);
    color: var(--text-main);
}

.lang-btn.active {
    background: rgba(255, 255, 255, 0.1);
    color: var(--text-main);
    border-color: var(--accent-color);
}