html {
    scroll-behavior: smooth; 
}



mark {
    background-color: rgb(255, 200, 0);
    color: black;
}



header {
    background-color: #0073ff;
    color: white;
    padding: 20px;
    text-align: center;
    width: auto;
     position: sticky;
  top: 0;
  z-index: 10;

}



body {
    font-family: Arial, sans-serif;
    line-height: 1.5;
    margin: 0;
    padding: 0;
    background-color: #f4f4f4;
    grid-template-rows: auto 1fr auto;
}



footer {
    display: grid;
    background: #333;
    color: white;
    padding: 20px;
    text-align: center;
}



.sidebar-left {
    float: left;
    width: 250px;
    height: 100vh; 
    background-color: #333;
    color: white;
    position: fixed; 
}

.sidebar-left h2 {
    text-align: center;
    padding: 15px 0;
}

.sidebar-left ul {
    list-style-type: none; 
    padding: 0;
}

.sidebar-left ul li {
    padding: 10px 15px;
}

.sidebar-left ul li a {
    color: white;
    text-decoration: none;
    display: block;
}

.sidebar-left ul li a:hover {
    background-color: #575757;
}



.container {
    position: relative; 
    margin-left: 260px;
    max-width: 800px;
    margin: auto;
    padding: 20px;
    background-color: white;
    border-radius: 5px;
    box-shadow: 0 2px 5px rgba(0,0,0,0.1);
    min-height: 85vh;

}




footer {
    text-align: center;
    padding: 10px;
    background-color: #0073ff;
    color: white;
    position: relative;
    bottom: 0px;
    left: 0;
    width: auto;
}



button {
    height: 42px;
	border: none;
	background: #3a7999;
	color: #f2f2f2;
	padding: 10px;
	font-size: 18px;
	border-radius: 5px;
	position: relative;
	box-sizing: border-box;
	transition: all 500ms ease; 
}


button:hover {
	background: rgba(0,0,0,0);
	color: #3a7999;
	box-shadow: inset 0 0 0 3px #3a7999;
}

#text {
    display: none; 
    margin-top: 10px;
}

#text2 {
    display: none; 
    margin-top: 10px;
}

.fraction {
    display: inline-block;
    text-align: center;
    vertical-align: middle;
}

.fraction > span {
    display: block;
}

.fraction > span:nth-child(2) {
    border-top: 1px solid black; 
}



.images {
    width: 800px;
    height: 600px;

}


ol {
	list-style-type: none; 
	counter-reset: num;
	margin: 0 0 0 45px;
	padding: 15px 0 5px 0;
	font-size: 18px;
}

ol li {
	position: relative;	
	margin: 0 0 0 0;
	padding: 0 0 10px 0;
	line-height: 1.4;
}

ol li:before {
	content: counter(num); 
	counter-increment: num;
	display: inline-block;
	position: absolute;
	top: 0;
	left: -38px;
	width: 28px;
	height: 28px;
	background: #00a6ff;
	color: #fff;
	text-align: center;
	line-height: 28px;
	font-size: 18px;
}



a {
    padding: 2px; 
    text-decoration: none; 
    color: #00a6ff;
}

a:hover {
    background: #f73; 
    color: yellow; 
}


.question {
     margin-bottom: 20px;
}

.result {
    margin-top: 10px;
    font-weight: bold;
}

.hidden {
    display: none;
}

.indicator {
    margin-left: 10px;
    font-weight: bold;
}

.correct {
    color: green;
}

.incorrect {
    color: red;
}

.input-correct {
    border-color: green;
    background-color: #e6ffe6; 
        }
.input-incorrect {
    border-color: red;
    background-color: #ffe6e6; 
        }
input{
    height: 30px;
}