* { box-sizing: border-box; }
body {
    margin: 0;
    font-family: Arial, sans-serif;
    background: #0f1117;
    color: #f5f7fb;
}
a { color: #ffffff; }
.nav {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 18px 5%;
    border-bottom: 1px solid #252a35;
    background: #121620;
}
.brand {
    font-weight: 800;
    text-decoration: none;
    font-size: 20px;
}
.nav-links a {
    margin-left: 18px;
    text-decoration: none;
    color: #cbd3e1;
}
.container {
    width: min(1150px, 92%);
    margin: 0 auto;
    padding: 36px 0;
}
.hero {
    display: flex;
    justify-content: space-between;
    gap: 20px;
    align-items: center;
    margin-bottom: 24px;
}
.hero h1 { margin-bottom: 8px; }
.grid { display: grid; gap: 22px; }
.grid.two { grid-template-columns: 1fr 1fr; }
.card, .auth-card {
    background: #171b26;
    border: 1px solid #2a3040;
    border-radius: 18px;
    padding: 24px;
    box-shadow: 0 14px 40px rgba(0,0,0,.2);
}
.auth-card {
    max-width: 480px;
    margin: 50px auto;
}
label {
    display: block;
    margin-top: 14px;
    color: #cbd3e1;
    font-size: 14px;
}
input, textarea, select, button {
    width: 100%;
    padding: 14px;
    margin-top: 8px;
    border-radius: 12px;
    border: 1px solid #343b4d;
    background: #10131a;
    color: #ffffff;
    font-size: 15px;
}
textarea { min-height: 120px; resize: vertical; }
button, .button-link {
    display: inline-block;
    background: #ffffff;
    color: #10131a;
    border: none;
    font-weight: 800;
    cursor: pointer;
    text-decoration: none;
    padding: 12px 16px;
    border-radius: 12px;
    margin-top: 12px;
}
button:hover, .button-link:hover { opacity: .9; }
.danger-link {
    display: inline-block;
    margin-left: 12px;
    color: #ff8c8c;
}
.muted { color: #9aa6bc; }
.alert {
    background: #3a1f25;
    border: 1px solid #8a3443;
    color: #ffd8de;
    padding: 12px;
    border-radius: 10px;
    margin: 14px 0;
}
.list-item {
    padding: 16px 0;
    border-bottom: 1px solid #2a3040;
}
.list-item:last-child { border-bottom: none; }
#chat {
    height: 520px;
    overflow-y: auto;
    padding: 18px;
    background: #10131a;
    border-radius: 16px;
    border: 1px solid #282f3f;
    margin-bottom: 16px;
}
.message {
    padding: 14px;
    border-radius: 14px;
    margin-bottom: 12px;
    white-space: pre-wrap;
    line-height: 1.5;
}
.message.user {
    background: #2e3850;
    margin-left: 20%;
}
.message.assistant {
    background: #202638;
    margin-right: 20%;
}
.final-prompt { min-height: 280px; }
@media (max-width: 800px) {
    .grid.two { grid-template-columns: 1fr; }
    .hero { flex-direction: column; align-items: flex-start; }
    .message.user, .message.assistant { margin-left: 0; margin-right: 0; }
}