style.css

@font-face {
    font-family: "Source Code Pro";
    src: url(./fonts/SourceCodeVariable-Roman.ttf);
}

* { box-sizing: border-box; }

[data-theme="dark"] {
    --bg-color: #002b36;
    --text-color: #93a1a1;
}

[data-theme="light"] {

}

html, body {
    width: 100%;
    height: 100%;
    padding: 0;
    margin: 0;
    font-family: "Source Code Pro", monospace;
}

body {
    font-size: 0.7em;
    background: black;
    color: white;
    display: grid;
    grid-template-columns: 300px auto;
    grid-template-rows: 72px auto 26px;
    grid-template-areas: "registers title"
                         "devices assembly"
                         "footer status";
}

/* define grid areas */
main { grid-area: assembly; }
aside { grid-area: devices; }
#registers { grid-area: registers; }
#status { grid-area: status; }
footer {grid-area: footer;}
header { grid-area: title; }

/* header-area styles */
header {
    background: linear-gradient(#000, transparent);
    height: 100%;
}

header h1 {
    padding: 0;
    margin: 0;
    text-transform: lowercase;
}

header p {
    margin: 0;
    padding: 0;
    text-transform: lowercase;
}

header ul {
    list-style: none;
    margin: 0;
    padding: 0;
    height: 100%;
    margin-left: 5px;r
}

header li {
    display: inline-block;
    background: linear-gradient(#C8C8C8, #FFFFFF);
    border: 1px solid grey;
    box-shadow: 1px black;
    width: 74px;
    height: 30px;
    text-align: center;
    margin-top: 5px;
    padding-top: 7px;
}

header li a {

    text-align: right;
    padding: 5px;
}


#registers tr {
    white-space: pre;
}

#registers.decimal {
    margin-right: 10px;
}


/* assembly-area styles */
main {
    display: flex;
    flex-direction: column;
    height: 100%;
    background: var(--bg-color);
    border-top-left-radius: 10px;
}

main textarea {
    resize: none;
    padding: 0;
    margin: 0;
    border: none;
    background: transparent;
    font-family: monospace;
    color: var(--text-color);
    font-size: 16px;
    outline: none;
    margin: 10px;
    height: 100%;
    width: 100%;
}

/* device-area styles */
aside {
    overflow: auto;
}

#ram {
    text-transform: uppercase;
}

#ram table {
    font-size: 0.9em;
}

#ram thead {
    background: black;
    text-align: right;
}

#ram tbody tr td:first-child {
    background: black;
}

#ram .last-set {
    background-color: magenta;
    color: white;
}

/* dohdiudhnd */

#status {
    display: grid;
    grid-template-columns: auto 80px;
}

#status.good {
    background-color: green;
}

#status.bad {
    background: red;
}

#status p {
    grid-column: 1;
    grid-row: 1;
    padding: 6px;
    margin: 0;
}

#status button {
    grid-column: 2;
    grid-row: 1;
}