style.css

:root {
    --content-max-width: 800px;
    --header-height: 77px;
    --editor-min-height: 1000px;
    --header-offset: 25px;
    --light-gray: #999;
}

html {
    min-width: 380px;
    box-sizing: border-box;
    font-family: Consolas, monospace;
    font-weight: 400;
}

body {
    padding: 0;
}

*, *:before, *:after {
    box-sizing: inherit;
    margin: 0;
}

.background {
    box-shadow: 0 0 1000px 600px hsla(0, 0%, 0%, .08);
    position: fixed;
    top: 0;
    width: 100vw;
    z-index: -2;
}

header {
    height: var(--header-height);
    background-color: white;
    box-shadow: 0 0 2px 2px rgba(0, 0, 0, .1);
    position: fixed;
    width: 100vw;
    z-index: 3;
    display: flex;
    flex-direction: row;
    justify-content: space-between;
    align-items: center;
}

header button {
    padding: 15px 20px;
    width: 100px;
}

header button:first-child {
    margin-left: 15px;
}

header button:last-child {
    margin-right: 15px;
}

.btn {
    border: 0;
    background-color: #f0f3f5;
    font-family: Consolas, monospace;
    transition: width 0.1s ease-out,
                height 0.1s ease-out;
    border-radius: 1px;
    outline: 0;
}

.btn:hover {
    cursor: pointer;
    box-shadow: 1px 1px 2px 2px rgba(0, 0, 0, .12);
    transition: width 0.05s ease-in,
                height 0.05s ease-in;
    transform: scale(1.02);
}

button::-moz-focus-inner {
  border: 0;
}

h1 {
    text-align: center;
    font-family: 'Great Vibes', cursive;
    margin: 0;
    font-size: 60px;
    height: 100%;
}

#file-name {
    text-align: center;
    font-family: Consolas, monospace;
    font-size: 30px;
    border: 0;
    outline: 0;
    width: 100%;
    margin: 50px auto 15px;
    background: transparent;
    border: 1px dotted transparent;
}

#file-name::placeholder {
    font-weight: 200;
    color: var(--light-gray);
}

#file-name:invalid {
    border: 1px dotted transparent;
    border-bottom-color: tomato;
    box-shadow: none;
}

.menu-background {
    height: 100vh;
    width: 100vw;
    position: fixed;
    top: 0;
    left: 0;
    z-index: 2;
    background: tomato;
    display: flex;
    justify-content: center;
    align-items: flex-start;
    overflow-y: scroll;
}

.menu {
    z-index: 3;
    background: white;
    padding: 10px;
    box-shadow: 2px 2px 2px 2px rgba(0, 0, 0, .1);
    min-width: 300px;
    width: 90vw;
    max-width: 600px;
    margin-top: calc(var(--header-height) + var(--header-offset));
}

.menu h2,
.menu p {
    text-align: center;
    margin-bottom: 20px;
}

.menu h2 {
    font-size: 28px;
    margin-bottom: 10px;
}

#file-list {
    list-style: none;
    padding: 0;
}

#file-list li {
    padding: 8px 14px;
    margin: 15px;
    height: 54px;
    display: flex;
    position: relative;
    justify-content: space-between;
    align-items: center;
}

#file-list .file-actions {
    display: flex;
    align-items: center;
}

#file-list li:hover button,
#file-list li:hover span {
    justify-content: center;
    visibility: visible;
}

#file-list li:hover span {
    cursor: help;
}

#file-list li:first-child {
    margin-top: 0;
}

#file-list button,
#file-list span {
    display: flex;
    align-items: center;
    visibility: hidden;
    height: 40px;
    color: #222;
    font-size: 20px;
    outline: 0;
    padding: 0 10px;
    border-radius: 50%;
    width: 40px;
    padding: 0;
    margin: 0 2px;
}

#file-list li.deleted-file {
    cursor: default;
}

#last-save {
    position: absolute;
    top: 15px;
    right: 20px;
    font-style: italic;
    color: var(--light-gray);
}

#last-save:empty,
#file-list:empty {
    display: none;
}

.file-list-toggle {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin: 10px auto 20px;
    width: 200px;
    padding: 5px;
}

.file-list-toggle:hover {
    background: #f0f3f5;
}

.file-list-toggle label {
    flex: 1;
    font-size: 16px;
    align-self: center;
}

.file-list-toggle label,
.file-list-toggle input {
    cursor: pointer;
}

[data-tooltip] {
    position: relative;
    z-index: 2;
    cursor: pointer;
}

/* Hide the tooltip content by default */
[data-tooltip]:before,
[data-tooltip]:after {
    visibility: hidden;
    opacity: 0;
    pointer-events: none;
}

/* Position tooltip above the element */
[data-tooltip]:before {
    position: absolute;
    bottom: 115%;
    left: 50%;
    margin-bottom: 5px;
    margin-left: -100px;
    padding: 7px;
    width: 200px;
    border-radius: 3px;
    background-color: #000;
    background-color: hsla(0, 0%, 20%, 0.9);
    color: #fff;
    content: attr(data-tooltip);
    text-align: center;
    font-size: 14px;
    line-height: 1.2;
}

/* Triangle hack to make tooltip look like a speech bubble */
[data-tooltip]:after {
    position: absolute;
    bottom: 115%;
    left: 50%;
    margin-left: -5px;
    width: 0;
    border-top: 5px solid #000;
    border-top: 5px solid hsla(0, 0%, 20%, 0.9);
    border-right: 5px solid transparent;
    border-left: 5px solid transparent;
    content: " ";
    font-size: 0;
    line-height: 0;
}

/* Show tooltip content on hover */
[data-tooltip]:hover:before,
[data-tooltip]:hover:after {
    visibility: visible;
    opacity: 1;
}

input[type="checkbox"] {
    -moz-appearance: none;
    -webkit-appearance: none;
    appearance: none;
    width: 25px;
    height: 25px;
    background: white;
    border: 2px solid var(--light-gray);
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 2px;
    outline: 0;
}

input[type="checkbox"]::after {
    font-weight: 400;
    font-size: 22px;
    margin-bottom: 1px;
}

input[type="checkbox"]:checked::after {
    content: '✓';
    color: black;
}

input[type="checkbox"]:not(:checked):hover::after {
    content: '✓';
    color: var(--light-gray);
}

.content-wrapper {
    position: absolute;
    overflow-y: scroll;
    top: var(--header-height);
    left: 0;
    right: 0;
    bottom: 0;
}

main {
    padding: 0 50px 35px;
    max-width: var(--content-max-width);
    display: flex;
    flex: 1;
    flex: 1 1 auto;
    flex-direction: column;
    min-height: 1000px;
    margin: var(--header-offset) auto 100px;
}

/*
Credit for paper effect: https://www.sitepoint.com/pure-css3-paper-curls/
Below is my slightly modified version.
*/
.paper {
    position: relative;
	background-color: #fff;
	box-shadow: 0 0 5px rgba(0, 0, 0, .2), inset 0 0 100px rgba(0, 0, 0, .05);
}

.paper:before,
.paper:after {
	position: absolute;
	width: 40%;
	height: 10px;
	content: ' ';
	left: 12px;
	bottom: 14px;
	background: transparent;
	transform: skew(-5deg) rotate(-5deg);
	box-shadow: 0 6px 12px rgba(0, 0, 0, .3);
	z-index: -1;
}

.paper:after {
	left: auto;
	right: 12px;
	transform: skew(5deg) rotate(5deg);
}

textarea {
    background: transparent;
    outline: none;
    border: none;
    padding: 10px 15px;
    min-width: 100%;
    min-height: calc(var(--editor-min-height) - 50px);
    resize: none;
    font-size: 20px;
    letter-spacing: .6px;
    font-family: 'Crimson Text', serif;
    overflow-y: hidden;
}

.unselectable {
    -webkit-user-select: none;
    -moz-user-select: none;
    -ms-user-select: none;
    -o-user-select: none;
    user-select: none;
}

.no-scroll {
    overflow: hidden;
}

.hidden {
    display: none;
}

@media screen and (max-width: 800px) {
    #file-name {
        font-size: 27px;
    }

    main {
        margin: 0;
        padding: 0 20px 35px;
    }

    textarea {
        font-size: 18px;
    }
}

@media screen and (max-width: 550px) {
    :root {
        --header-height: 50px;
        --header-offset: 15px;
    }

    header h1 {
        font-size: 40px;
    }

    header button {
        padding: 12px 5px;
        width: 80px;
    }

    header button:first-child {
        margin-left: 5px;
    }

    header button:last-child {
        margin-right: 5px;
    }

    #file-name {
        font-size: 24px;
    }

    #last-save {
        font-size: 14px;
        right: 15px;
    }

    main {
        padding: 0 0 35px;
    }

    textarea {
        font-size: 16px;
    }
}