html {
  box-sizing: border-box;
  background-color: #f1f2f3;
}
*, *::before, *::after {
  box-sizing: inherit;
}
body {
	width: 1200px;
	margin: auto;
}
.center{
	position: relative;
	display: flex;
	align-items: center;
	justify-content: center;
}
.main{
    border-radius: 3px;
    padding: 30px 0;
	min-height: 200px;
	margin: 20px auto;
    overflow: hidden;
	background: #ffffff;
	text-align: center;
	display: flex;
	flex-direction: column;
	flex-wrap: wrap;
	align-content: center;
	justify-content: center;
	align-items: center;
}
.ipts{
	margin-bottom: 25px;
	font-size: 14px;
	color: #333;
}
.ipts input{
	margin-right: 25px;
	margin-left: 5px;
	outline: none;
	height: 36px;
	border: 1px solid #ddd;
	padding: 0 10px;
	width: 150px;
	border-radius: 5px;
	font-size: 14px;
	color: #666;
}
.handle{
	margin-top: 25px;
	user-select: none;
}
.handle button{
	margin: 0 20px;
	height: 40px;
	padding: 0 25px;
	color: #fff;
	background-color: #409EFF;
	border: none;
	border-radius: 4px;
	outline: none;
	cursor: pointer;
}
.handle #reset{
	background-color: #67C23A;
}
.handle #full-screen{
	background-color: #E6A23C;
}
button img {
	width: 20px;
	height: 20px;
	vertical-align: middle;
	margin-left: 10px;
}
/*-------提示---------*/
.ts{
	margin: 20px 0;
}
.ts .title{
	font-size: 18px;
	color: #333;
	margin: 20px 0;
	font-weight: bold;
}
.ts p{
	color:#666;
	margin: 0;
	padding: 0;
	line-height: 30px;
	background: #ffffff;
	padding: 10px;
}
.ts p span{
	color:#F16F5C;
}

/* ------------ 计时器 ------------ */
#timer {
	position: relative;
	width: 60%;
	background-color: black;
	border-radius: 0.5rem;
	user-select: none;
}
#timer::after {
	content: "";
	display: block;
	margin-top: calc(270 / 480 * 100%);
}
#score-board {
	display: flex;
	justify-content: center;
	align-items: center;
	position: absolute;
	width: 100%;
	height: 100%;
}
#minute, #second {
	position: relative;
	width: calc(200 / 480 * 100%);
	margin: calc(5 / 480 * 100%);
	perspective: 400vw;
}
#minute::after, #second::after {
	content: "";
	display: block;
	margin-top: 100%;
}
.upper, .lower {
	position: absolute;
	width: 100%;
	height: 50%;
	background-color: #212121;
	overflow: hidden;
}
.upper {
	top: 0;
	border-bottom: solid black 0.2rem;
	border-radius: 0.5rem 0.5rem 0 0;
}
.lower {
	bottom: 0;
	border-top: solid black 0.2rem;
	border-radius: 0 0 0.5rem 0.5rem;
}
.upper img, .lower img {
	display: block;
	position: absolute;
	width: 100%;
	height: auto;
}
.upper img {
	top: 0;
}

.lower img {
	bottom: 0;
}
/* ------------ 动画 ------------ */
.animate-box {
	position: absolute;
	width: 100%;
	height: 50%;
	top: 0;
	transform-origin: bottom;/* 转动轴 */
	transform-style: preserve-3d;/* 在空间中变形，从而背面可见 */
}
.animate-box>* {
	height: 100%;
	backface-visibility: hidden;
}

.animate-box>.lower {
	transform-origin: center;
	transform: rotateX(180deg);
}
.animate {
	transition: transform 0.5s linear;
	transform: rotateX(-180deg);
}