body {
    background-color: #ffe2aa;
}

p {
    background-color: #803e3e;
}

span {
    color: #f00;
}

/*seletor grupo*/
h1, h2, h3, mark {
    font-size: 20pt;
    color: #0f0;
    font-weight: bold;
}

mark {
    background-color: #fd7474;
    color: #fff;
}

section p {
    width: 400px;
}

section>p {
    text-align: center;
}

#c1 {
    border: 2px dotted #000;
}

#c2 {
    border: 10px dashed #f00;
}

#c3 {
    border: 20px double #0f0;
}

.caixa {
    width: 500px;
    height: 500px; /*quadrado*/
    margin: auto; /*centraliza quadrado*/
    border-radius: 250px 0px 250px 0px;
    box-shadow: 0px 0px 15px #000; /*sombra na caixa*/
}
mark {
    display: inline-block;
    text-align: center;
    
}
.caixa_mark {
    width: 150px;
    height: 80px;
}