* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Comic Relief', -apple-system, BlinkMacSystemFont, "Segoe UI", "Roboto", "Helvetica Neue",
        "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei",
        Arial, sans-serif;
}

/* 页面布局 */
.content {
    position: absolute;
    top: 10%;
    left: 50%;
    transform: translate(-50%);
    display: flex;
    flex-direction: column;
    gap: 12px;

}

/* 问候 */
.greeting {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 5px;
}

/* 纸飞机背景位置 */
paper-plane {
    /* 将 paper-plane 组件本身抽离文档流 */
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: -1;
    /* 把它放在最底层，防止遮挡时钟、搜索栏等内容 */
}

/* footer */
footer {
    white-space: nowrap;
    position: absolute;
    display: flex;
    justify-content: center;
    align-items: center;
    bottom: 2%;
    left: 50%;
    transform: translate(-50%);
}

footer a {
    text-decoration: none;
    color: inherit;
}

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

@media screen and (max-width: 550px) {
    footer {
        font-size: 10px;
    }
}

/* 状态类 */
.btn-active {
    background-color: rgba(0, 0, 0, 0.1);
}

.is-hidden {
    display: none;
}

.no-select {
    -webkit-user-select: none;
    -moz-user-select: none;
    -ms-user-select: none;
    user-select: none;
}