body {
    margin: 0;
    background-color: #212121;
    font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
    color: #e4e4e7;
    display: flex;
    flex-direction: column;
    height: 100vh;
}

.topbar {
    background-color: #1c1c1c;
    height: 52px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0 28px;
    box-sizing: border-box;
}

.topbar-title {
    color: #e4e4e7;
    font-size: 20px;
    font-weight: bold;
}

.topbar-nav a {
    color: #e4e4e7;
    text-decoration: none;
    margin-left: 24px;
    font-size: 15px;
    transition: color 0.2s ease;
}

.topbar-nav a:hover {
    color: #00e676;
}

.chat-container {
    flex: 1;
    overflow-y: auto;
    padding: 20px 260px;
    display: flex;
    flex-direction: column;
    gap: 16px;
}

.message {
    max-width: 70%;
    padding: 14px 18px;
    border-radius: 8px;
    background-color: #383838;
    position: relative;
    transition: background-color 0.3s ease;
    word-break: break-word;
}

.message.user {
    align-self: flex-end;
    background-color: #2e2e2e;
}

.message.assistant {
    align-self: flex-start;
}

.message:hover {
    background-color: #444;
}

.copy-button {
    position: absolute;
    bottom: -28px;
    right: 10px;
    font-size: 13px;
    color: #00e676;
    background: none;
    border: none;
    cursor: pointer;
    opacity: 0;
    transition: opacity 0.3s ease 1s; /* 延迟1s淡出 */
    pointer-events: none;
}

.message:hover .copy-button {
    opacity: 1;
    pointer-events: auto;
    transition-delay: 0s; /* 立即显现 */
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(4px); }
    to { opacity: 1; transform: translateY(0); }
}

.input-footer {
    display: flex;
    background-color: #1c1c1c;
    padding: 12px 260px;
    border-top: 1px solid #2a2a2a;
}

#user-input {
    flex: 1;
    padding: 10px 14px;
    font-size: 15px;
    background-color: #303030;
    border: 1px solid #5e5f6b;
    color: #e4e4e7;
    border-radius: 6px;
    resize: none;
    outline: none;
}

#send-button {
    margin-left: 12px;
    background-color: #565869;
    border: none;
    color: #fff;
    font-size: 15px;
    padding: 10px 18px;
    border-radius: 6px;
    cursor: pointer;
    transition: background-color 0.3s ease;
}

#send-button:hover {
    background-color: #6b6d7e;
}

/* Markdown code styling */
.message pre {
    background-color: #2e2e2e;
    padding: 12px;
    border-radius: 6px;
    overflow-x: auto;
}

.message code {
    color: #ffcc00;
}

/* 滚动条整体轨道 */
::-webkit-scrollbar {
    width: 8px;
    height: 8px;
}

/* 滚动条轨道背景 */
::-webkit-scrollbar-track {
    background: #212121;
}

/* 滚动条本体 */
::-webkit-scrollbar-thumb {
    background-color: #444;
    border-radius: 4px;
}

/* 鼠标悬停时加深颜色 */
::-webkit-scrollbar-thumb:hover {
    background-color: #555;
}

@media (max-aspect-ratio: 4/3), (max-width: 768px) {
    .chat-container {
        padding: 20px 10px;
    }

    .input-footer {
        padding: 12px 10px;
    }
}