@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700&display=swap');

:root {
    --primary-color: #007aff;
    --primary-hover: #0063d1;
    --background-color: #f5f5f7;
    --text-color: #1d1d1f;
    --card-background: #ffffff;
    --subtle-text: #86868b;
    --border-color: rgba(134, 134, 139, 0.2);
    --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.04);
    --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.06), 0 12px 24px rgba(0, 0, 0, 0.04);
    --shadow-lg: 0 8px 24px rgba(0, 0, 0, 0.08), 0 16px 40px rgba(0, 0, 0, 0.06);
    --gradient-blue: linear-gradient(135deg, #007aff, #5ac8fa);
    --gradient-green: linear-gradient(135deg, #34c759, #30d158);
    --gradient-orange: linear-gradient(135deg, #ff9500, #ff6723);
}

@media (prefers-color-scheme: dark) {
    :root {
        --primary-color: #0a84ff;
        --primary-hover: #409cff;
        --background-color: #000000;
        --text-color: #f5f5f7;
        --card-background: #1c1c1e;
        --border-color: rgba(134, 134, 139, 0.3);
        --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.2);
        --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.3), 0 12px 24px rgba(0, 0, 0, 0.2);
        --shadow-lg: 0 8px 24px rgba(0, 0, 0, 0.4), 0 16px 40px rgba(0, 0, 0, 0.3);
    }
}

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

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    background-color: var(--background-color);
    color: var(--text-color);
    line-height: 1.7;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

/* Header */
header {
    text-align: center;
    padding: 3.5rem 1rem 1.5rem;
    position: relative;
}

header h1 {
    font-size: 2rem;
    font-weight: 700;
    margin: 0 0 0.25rem 0;
    letter-spacing: -0.03em;
    background: linear-gradient(135deg, var(--text-color) 0%, var(--subtle-text) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

header p {
    color: var(--subtle-text);
    font-size: 1rem;
    font-weight: 400;
}

/* Language Toggle */
.lang-toggle {
    position: absolute;
    top: 1.5rem;
    right: 1.5rem;
    background-color: var(--card-background);
    border: 1px solid var(--border-color);
    padding: 0.5rem 1rem;
    border-radius: 20px;
    cursor: pointer;
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--text-color);
    transition: all 0.2s ease;
    box-shadow: var(--shadow-sm);
    font-family: inherit;
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
}

.lang-toggle:hover {
    transform: translateY(-1px);
    box-shadow: var(--shadow-md);
    background-color: rgba(134, 134, 139, 0.05);
}

.lang-toggle:active {
    transform: translateY(0);
}

/* Navigation */
.nav-links {
    display: flex;
    justify-content: center;
    gap: 0.5rem;
    margin: 0 auto 2rem;
    max-width: 800px;
    padding: 0 1rem;
    flex-wrap: wrap;
}

.nav-links a {
    text-decoration: none;
    color: var(--subtle-text);
    font-size: 0.95rem;
    font-weight: 600;
    padding: 0.5rem 1.25rem;
    border-radius: 20px;
    transition: all 0.2s ease;
    font-family: inherit;
}

.nav-links a:hover {
    color: var(--text-color);
    background-color: rgba(134, 134, 139, 0.1);
}

.nav-links a.active {
    color: white;
    background-color: var(--primary-color);
}

/* Main Content */
main {
    flex: 1;
    max-width: 800px;
    margin: 0 auto;
    padding: 0 1rem 2rem;
    width: 100%;
}

/* Content Card */
.section-card {
    background-color: var(--card-background);
    border-radius: 18px;
    padding: 2.5rem;
    box-shadow: var(--shadow-md);
    animation: fadeIn 0.5s cubic-bezier(0.25, 0.46, 0.45, 0.94);
}

.section-card h2 {
    font-size: 1.5rem;
    font-weight: 700;
    margin-top: 0;
    margin-bottom: 1.5rem;
    border-bottom: 1px solid var(--border-color);
    padding-bottom: 0.75rem;
    letter-spacing: -0.02em;
}

.section-card h3 {
    font-size: 1.1rem;
    font-weight: 600;
    margin-top: 1.75rem;
    margin-bottom: 0.5rem;
}

.section-card p {
    margin-bottom: 0.75rem;
    color: var(--text-color);
    opacity: 0.9;
}

.section-card ul {
    padding-left: 1.5rem;
    margin-bottom: 0.75rem;
}

.section-card ul li {
    margin-bottom: 0.35rem;
    line-height: 1.6;
}

/* Contact Button */
.contact-action {
    text-align: center;
    margin-top: 2.5rem;
}

.contact-email {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    background: var(--gradient-blue);
    color: white;
    text-decoration: none;
    padding: 0.875rem 2rem;
    border-radius: 25px;
    font-weight: 600;
    font-size: 1.05rem;
    transition: all 0.3s cubic-bezier(0.25, 0.46, 0.45, 0.94);
    box-shadow: 0 4px 14px rgba(0, 122, 255, 0.3);
}

.contact-email:hover {
    transform: translateY(-2px) scale(1.02);
    box-shadow: 0 6px 20px rgba(0, 122, 255, 0.4);
}

.contact-email:active {
    transform: translateY(0) scale(0.98);
}

/* Footer */
footer {
    text-align: center;
    padding: 3rem 1rem 2rem;
    color: var(--subtle-text);
    font-size: 0.875rem;
}

footer a {
    color: var(--primary-color);
    text-decoration: none;
    font-weight: 500;
}

footer a:hover {
    text-decoration: underline;
}

/* Animation */
@keyframes fadeIn {
    from { opacity: 0; transform: translateY(12px); }
    to { opacity: 1; transform: translateY(0); }
}

@keyframes slideUp {
    from { opacity: 0; transform: translateY(20px); }
    to { opacity: 1; transform: translateY(0); }
}

/* Language visibility control */
body[data-lang="en"] .lang-ko { display: none !important; }
body[data-lang="ko"] .lang-en { display: none !important; }

.section-card p.lang-en, .section-card h2.lang-en, .section-card h3.lang-en,
.section-card p.lang-ko, .section-card h2.lang-ko, .section-card h3.lang-ko {
    display: block;
}

span.lang-en, span.lang-ko {
    display: inline;
}

/* Landing page cards */
.page-cards {
    display: grid;
    grid-template-columns: 1fr;
    gap: 1rem;
    max-width: 800px;
    margin: 0 auto;
    padding: 0 1rem 2rem;
}

.page-card {
    display: flex;
    align-items: center;
    gap: 1.25rem;
    background-color: var(--card-background);
    border-radius: 18px;
    padding: 1.75rem 2rem;
    text-decoration: none;
    color: var(--text-color);
    box-shadow: var(--shadow-md);
    transition: all 0.3s cubic-bezier(0.25, 0.46, 0.45, 0.94);
    animation: slideUp 0.5s cubic-bezier(0.25, 0.46, 0.45, 0.94) backwards;
}

.page-card:nth-child(1) { animation-delay: 0.05s; }
.page-card:nth-child(2) { animation-delay: 0.12s; }
.page-card:nth-child(3) { animation-delay: 0.19s; }

.page-card:hover {
    transform: translateY(-3px);
    box-shadow: var(--shadow-lg);
}

.page-card:active {
    transform: translateY(-1px);
}

.page-card .card-icon {
    font-size: 1.75rem;
    width: 56px;
    height: 56px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 14px;
    flex-shrink: 0;
    color: white;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
}

.page-card .card-icon.support-icon {
    background: var(--gradient-blue);
}

.page-card .card-icon.privacy-icon {
    background: var(--gradient-green);
}

.page-card .card-icon.terms-icon {
    background: var(--gradient-orange);
}

.page-card .card-content h3 {
    font-size: 1.1rem;
    font-weight: 600;
    margin: 0 0 0.25rem 0;
    letter-spacing: -0.01em;
}

.page-card .card-content p {
    font-size: 0.9rem;
    color: var(--subtle-text);
    margin: 0;
}

.page-card .card-arrow {
    margin-left: auto;
    color: var(--subtle-text);
    font-size: 1.25rem;
    flex-shrink: 0;
    transition: transform 0.2s ease;
}

.page-card:hover .card-arrow {
    transform: translateX(3px);
    color: var(--primary-color);
}

/* Back link */
.back-link {
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
    text-decoration: none;
    color: var(--primary-color);
    font-weight: 600;
    font-size: 0.95rem;
    margin-bottom: 1.5rem;
    padding: 0.25rem 0;
    transition: all 0.2s ease;
}

.back-link:hover {
    opacity: 0.8;
}

.back-link .arrow {
    font-size: 1.1rem;
    transition: transform 0.2s ease;
}

.back-link:hover .arrow {
    transform: translateX(-3px);
}

@media (max-width: 600px) {
    header {
        padding: 3rem 1rem 1rem;
    }
    header h1 {
        font-size: 1.6rem;
    }
    .section-card {
        padding: 1.75rem;
        border-radius: 14px;
    }
    .page-card {
        padding: 1.25rem 1.5rem;
        border-radius: 14px;
    }
    .lang-toggle {
        top: 1rem;
        right: 1rem;
        font-size: 0.8rem;
        padding: 0.4rem 0.8rem;
    }
    .nav-links a {
        font-size: 0.85rem;
        padding: 0.4rem 1rem;
    }
}