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

:root {
    --bg: #fafafa;
    --text: #2d2d2d;
    --accent: #e74c3c;
    --muted: #666;
    --card-bg: #fff;
    --border: #eee;
}

body {
    font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;
    background: var(--bg);
    color: var(--text);
    line-height: 1.7;
    min-height: 100vh;
}

.container {
    max-width: 720px;
    margin: 0 auto;
    padding: 3rem 1.5rem;
}

header {
    text-align: center;
    margin-bottom: 3rem;
}

.lang-toggle {
    position: absolute;
    top: 1.5rem;
    right: 1.5rem;
    display: flex;
    gap: 0.5rem;
}

.lang-btn {
    background: var(--card-bg);
    border: 1px solid var(--border);
    padding: 0.5rem 1rem;
    border-radius: 6px;
    cursor: pointer;
    font-size: 0.85rem;
    transition: all 0.2s ease;
}

.lang-btn:hover,
.lang-btn.active {
    background: var(--accent);
    color: white;
    border-color: var(--accent);
}

h1 {
    font-size: 2.5rem;
    font-weight: 300;
    margin-bottom: 0.5rem;
}

h1 span {
    color: var(--accent);
    font-weight: 600;
}

.subtitle {
    color: var(--muted);
    font-size: 1.1rem;
}

.intro {
    background: var(--card-bg);
    border-left: 4px solid var(--accent);
    padding: 1.5rem;
    border-radius: 0 8px 8px 0;
    margin-bottom: 2rem;
    box-shadow: 0 2px 12px rgba(0, 0, 0, 0.04);
}

h2 {
    font-size: 1.3rem;
    font-weight: 500;
    margin: 2rem 0 1rem;
    color: var(--text);
}

p {
    margin-bottom: 1rem;
}

.chat-example {
    background: var(--card-bg);
    border-radius: 12px;
    padding: 1.5rem;
    margin: 1.5rem 0;
    box-shadow: 0 2px 12px rgba(0, 0, 0, 0.04);
}

.chat-example.bad {
    border: 1px solid #ffcdd2;
}

.chat-example.good {
    border: 1px solid #c8e6c9;
}

.chat-label {
    font-size: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 1px;
    margin-bottom: 1rem;
    font-weight: 600;
}

.chat-label.bad {
    color: #c0392b;
}

.chat-label.good {
    color: #27ae60;
}

.message {
    display: flex;
    gap: 0.75rem;
    margin-bottom: 0.75rem;
    align-items: baseline;
}

.time {
    color: var(--muted);
    font-size: 0.85rem;
    font-family: 'Consolas', monospace;
    min-width: 40px;
}

.sender {
    font-weight: 600;
    min-width: 50px;
}

.sender.fred {
    color: #3498db;
}

.sender.alice {
    color: #9b59b6;
}

.benefits {
    background: linear-gradient(135deg, #e8f5e9 0%, #f1f8e9 100%);
    border-radius: 12px;
    padding: 1.5rem;
    margin: 1.5rem 0;
}

.benefits ul {
    list-style: none;
    padding-left: 0;
}

.benefits li {
    padding: 0.5rem 0;
    padding-left: 1.5rem;
    position: relative;
}

.benefits li::before {
    content: "✓";
    position: absolute;
    left: 0;
    color: #27ae60;
    font-weight: bold;
}

footer {
    text-align: center;
    margin-top: 4rem;
    padding-top: 2rem;
    border-top: 1px solid var(--border);
    color: var(--muted);
    font-size: 0.9rem;
}

.hidden {
    display: none;
}

@media (max-width: 600px) {
    h1 {
        font-size: 2rem;
    }

    .lang-toggle {
        position: static;
        justify-content: center;
        margin-bottom: 2rem;
    }

    .container {
        padding: 1.5rem 1rem;
    }
}