body {
    font-family: -apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,Oxygen-Sans,Ubuntu,Cantarell,"Helvetica Neue",sans-serif;
    font-weight: 400;
    max-width: 700px;
    margin: auto;
}

.header {
    padding: 20px;
    background-color: #EEE;
} .header h2, .header h3, .header p {
    margin: 10px 0;
} .header p {
    font-style: italic;
    font-size: 0.9rem;
}

h1,h2,h3,h4 {
    margin-top: 20px;
    margin-bottom: 0;
}
p, ul, ol {
    margin-top: 0;
    margin-bottom: 10px;
}

@font-face {
    font-family: computer-modern;
    font-style: normal;
    font-weight: 400;
    src: url('cmunrm.ttf');
  }

.exercises {
    padding: 5px;
} .exercises p, .exercises blockquote, .exercises ul, .exercises > span, .exercises ol {
    font-family: computer-modern;
    font-variant-ligatures: none;
    font-size: 16.7px;
    line-height: 1.333;
} .exercises blockquote {
    border-left: 3px solid #BBB;
    padding-left: 15px;
    padding-top: 5px;
    padding-bottom: 5px;
} .exercises p > b {
    font-size: 17px;
    letter-spacing: 0.1px;
}

code {
    font-family: Consolas;
}

.col2 {
    display: grid;
    grid-template-areas: 'a b';
    grid-gap: 15px;
} .col2 > :first-child {
    grid-area: a;
} .col2 > :last-child {
    grid-area: b;
}

.img-container {
    display: block;
    overflow: hidden;
    position: relative;
} .img-container > img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    vertical-align: middle;
}

table {
    color: #212529;
    border-collapse: collapse;
    display: inline-block;
    margin-bottom: 10px;
}
table th {
    vertical-align: bottom;
    border: 1px solid #343a40;
    border-bottom: 2px solid #57606a;
    background-color: #343a40;
    color: #FFF;
} table th, table td {
    padding: 0.5rem;
    padding-left: 0.61rem;
    vertical-align: top;
    min-width: 22px;
    text-align: left;
} table td {
    border: 1px solid #b7bbbe;
}

img {
    display: block;
    margin: 10px auto;
    max-width: 100%;
}

code.hljs   {
    margin: 10px 0;
}

.prooftree {
    display: flex;
    width: 100%;
}
.prooftree.centered {
    width: max-content;
    margin: auto;
}
.prooftree .rules {
    /* float: left; */
    margin-top: 15px;
}
.prooftree .lines span {
    display: block;
    border-bottom: 1px solid #000;
    text-align: center;
    padding: 1px 0px;
}
.prooftree .lines > span:last-child {
    border-bottom: none;
}
.prooftree .rules span {
    display: block;
    /* max-width: 10px; */
    font-size: 14px;
    margin-bottom: 6px;
    margin-left: 5px;
}