* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: "Microsoft Yahei", sans-serif;
}

body {
font-family: "Microsoft Yahei", sans-serif;
    /* ============= 核心修改：背景图片链接 ============= */
    /* 1. 替换 background-image 的 URL 地址 */
    /* 2. 建议修改背景尺寸为 cover 以铺满屏幕 */
    /* 3. 增加 no-repeat center center 保证居中且不重复 */
    background: url('https://study.zeroner.cn/bg.jpg') no-repeat center center fixed;
    background-size: cover; 
    /* ============= 背景修改结束 ============= */
    
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
}

.container {
    max-width: 600px;
    margin: 0 auto;
    height: 100vh;
    display: flex;
    flex-direction: column;
    padding: 20px;
}

.header {
    background: linear-gradient(to right, #64b5f6, #bbdefb);
    padding: 15px;
    border-radius: 20px;
    text-align: center;
    margin-bottom: 20px;
    box-shadow: 0 4px 8px rgba(0,0,0,0.1);
}

.header h1 {
    color: #000;
    font-size: 2rem;
    font-weight: 500;
}

.chat-container {
    flex: 1;
    overflow-y: auto;
    padding: 10px;
    margin-bottom: 20px;
    display: flex;
    flex-direction: column;
    gap: 15px;
}

/* 用户气泡（右侧） */
.chat-bubble.user {
    align-self: flex-end;
    background: #fff;
    border: 2px solid #000;
    border-radius: 20px 20px 0 20px;
    padding: 12px 20px;
    max-width: 70%;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
    position: relative;
}

.chat-bubble.user::after {
    content: '';
    position: absolute;
    right: -10px;
    bottom: 10px;
    width: 0;
    height: 0;
    border-left: 10px solid #fff;
    border-top: 10px solid transparent;
    border-bottom: 10px solid transparent;
}

/* AI气泡（左侧） */
.chat-bubble.ai {
    align-self: flex-start;
    background: #e3f2fd;
    border: 2px solid #000;
    border-radius: 20px 20px 20px 0;
    padding: 12px 20px;
    max-width: 70%;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
    position: relative;
}

.chat-bubble.ai::after {
    content: '';
    position: absolute;
    left: -10px;
    bottom: 10px;
    width: 0;
    height: 0;
    border-right: 10px solid #e3f2fd;
    border-top: 10px solid transparent;
    border-bottom: 10px solid transparent;
}

.footer {
    width: 100%;
    text-align: center;
}

.record-btn {
    width: 100%;
    padding: 20px;
    background: linear-gradient(to right, #64b5f6, #bbdefb);
    border: 3px solid #0d47a1;
    border-radius: 20px;
    font-size: 1.8rem;
    font-weight: 500;
    color: #000;
    cursor: pointer;
    transition: all 0.2s ease;
    box-shadow: 0 6px 12px rgba(0,0,0,0.15);
}

.record-btn:active {
    transform: scale(0.98);
    box-shadow: 0 3px 6px rgba(0,0,0,0.1);
    background: linear-gradient(to right, #42a5f5, #90caf9);
}

/* 滚动条美化 */
.chat-container::-webkit-scrollbar {
    width: 6px;
}

.chat-container::-webkit-scrollbar-track {
    background: rgba(255,255,255,0.3);
    border-radius: 3px;
}

.chat-container::-webkit-scrollbar-thumb {
    background: rgba(0,0,0,0.2);
    border-radius: 3px;
}