*{box-sizing: border-box;
margin: 0;
padding: 0;
}

body {
font-family: 'Open Sans', sans-serif;
background-color: whitesmoke;
}

nav {
    position: sticky;
    top: 0;
    z-index: 10;
    height: 60px;
    line-height: 60px;
    background-color: white;
    text-align: center;

}
.wrapper{
    margin: 0 auto;
    width: 100%;
    max-width: 1200px;
}

.burger-icon {
    display: block;
    margin-left: auto;
    padding: 0 30px;
    background: none;
    border: none;
    font-size: 30px;
    line-height: 60px;
    cursor: pointer;
}

.nav-items {
    display: none;
}


.nav-items a {
    padding: 0 30px;
    text-decoration: none;
    text-transform: uppercase;
    font-weight: bold;
    color: #333;
    transition: color 0.3s;
}

.nav-items a:hover {
    color: #09f;
}

.header {position: relative;
height: 330px;
background-image: url('../img/m1.jpg');
background-size: cover;
background-position: center;
}


.wolf-bg {
 position: absolute;
 width: 100%;  
 height: 100%;
 background-color: rgba(0,0,0,.8);
}


.didactic-bg {
    position: absolute;
    width: 100%;  
    height: 100%;
    background-color: rgba(0,0,0,.7); 
    }

    .publications-bg {
        position: absolute;
        width: 100%;  
        height: 100%;
        background-color: rgba(0,0,0,.7); 
        }
    

   .didactic a {
    text-decoration: none;
    color: azure;
   }

   
.didactic a:hover{
    color:aqua
}

   .publications a {
    text-decoration: none;
    color: azure;
   }

   .publications a:hover{
    color:aqua
}

.publications-bg {
    position: absolute;
    width: 100%;  
    height: 100%;
   }

.publications {
    background-color: rgba(0,0,0,.7); 
}

.wolf-text {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%,-50%);
    color: white;
}

.publications-text {
    position: absolute;
    width: 1000px;
    top: 50%;
    left: 50%;
    transform: translate(-50%,-50%);
    color: white;
}

.wolf-text h1 {
    margin-bottom: 5px;
    text-shadow: 0px 3px 5px #000;
    color: #ddd;
}

.publications-text h1 {
    margin-bottom: 5px;
    text-shadow: 0px 3px 5px #000;
    color: #ddd;
}

.wolf-text span {
    text-transform: uppercase;
    color: #09f;
}

.publications-text span {
    text-transform: uppercase;
    color: #09f;
}

.section-title {
    margin-bottom: 20px;
    text-transform: uppercase;
    text-align: center;
    color: black;
}

main {
    margin: 80px 0;
}

.about-us-info {
    padding: 50px;
    height: 200px;
    margin-bottom: 30px;
    text-align: center;
  color:black;
}

.about-us {
    background-color: #ddd;
   
}

.product :hover h3 {
    transform: scale(1.6);
}

.math{
    padding: auto;
   font-size: 20px;
   margin-bottom: 30px;
}

.didactic {
    position: relative;
    height: 400px;
    background-image: url('../img/pi.jpg');
    background-size: cover;
    background-position: center;
    text-align: center;
  
}

.didactic h3 {
    text-transform: uppercase;
    transition: transform .3s;
}

.publications {
    margin-top: 20px;
    position: relative;
    height: 400px;
    background-image: url('../img/publikacje.jpg');
    background-size: cover;
    background-position: center;
    text-align: center;
  
}

.publications a:hover{
    color:aqua
}

.publications h3 {
    text-transform: uppercase;
    transition: transform .3s;
}

.contact {
    margin-top: 20px;
    text-align: center;
}

.contact h3 {
    margin: 20px 0 5px;
    text-transform: uppercase;
}

footer {
    padding: 30px 10px;
    text-align: center;
    background-color: #ddd;
}

@media (min-width: 738px) {
    .burger-icon {
        display: none;
    }
    .nav-items {
        display: block;
    }
    .header {
        background-image: url(../img/m5.jpg);
    }
}