index.css

:root {
  --font-color: #090821;
  --bg-color: #dae5ed;
  --afont-color: #fc2f70;
  --dbg-color: rgba(0, 0, 0, 0.1);
  --dbgh-color: rgba(0, 0, 0, 0.2);
  --dbga-color: rgba(0, 0, 0, 0.3);
}

[data-theme="dark"] {
  --font-color: #f8f8f2;
  --bg-color: #282a36;
  --afont-color: #3cefff;
  --dbg-color: rgba(255, 255, 255, 0.1);
  --dbgh-color: rgba(255, 255, 255, 0.2);
  --dbga-color: rgba(255, 255, 255, 0.3);
}

* {
  box-sizing: border-box;
  outline: 0;
  border: 0;
}

::-webkit-scrollbar {
  width: 4px;
  height: 4px;
}

::-webkit-scrollbar-thumb {
  background: var(--dbg-color);
}

::-webkit-scrollbar-thumb:hover {
  background: var(--dbgh-color);
}

::-webkit-scrollbar-thumb:active {
  background: var(--dbga-color);
}

::placeholder {
  color: var(--font-color);
}

::selection {
  background: #c6d5dd;
}

@keyframes fadein {
  from {
    opacity: 0;
  }

  to {
    opacity: 1;
  }
}

a {
  display: inline-flex;
  border-bottom: 2px solid var(--afont-color);
  color: inherit;
  text-decoration: none;
  align-items: center;
  justify-content: center;
}

body {
  margin: 0;
  width: 100%;
  height: 100vh;
  background-color: var(--bg-color);
  color: var(--font-color);
  font-size: 18px;
  font-family: "Roboto Mono", "SF Mono", "Lucida Console", Monaco, monospace;
  line-height: 2;
  animation: fadein 0.2s;
  -webkit-tap-highlight-color: transparent;
  -webkit-touch-callout: none;
  -webkit-user-select: none;
  user-select: none;
}

.container {
  display: flex;
  flex-direction: column;
  width: 100%;
  height: 100%;
}

header,
footer {
  z-index: 1;
  display: flex;
  padding: 8px 16px;
  font-weight: 700;
  align-items: center;
}

.tools {
  display: flex;
  overflow-x: auto;
  white-space: nowrap;
  align-items: center;
  justify-content: space-between;
  flex-grow: 1;
}

.tools span {
  padding: 0 8px;
}

.file,
button {
  padding: 8px 16px;
  background-color: transparent;
  color: var(--afont-color);
  font-weight: 700;
  font-size: 18px;
  font-family: "Roboto Mono", "SF Mono", "Lucida Console", Monaco, monospace;
  cursor: pointer;
}

button[disabled] {
  opacity: 0.5;
  pointer-events: none;
}

.trigger {
  cursor: pointer;
}

.modal {
  position: fixed;
  top: 0;
  left: 0;
  z-index: 99;
  visibility: hidden;
  width: 100%;
  height: 100%;
  background-color: rgba(0, 0, 0, 0.6);
  opacity: 0;
  transition: all 0.2s;
  transform: scale(1.05);
}

.show-modal {
  visibility: visible;
  opacity: 1;
  transition: all 0.2s;
  transform: scale(1);
}

.modal-content {
  position: absolute;
  top: 50%;
  left: 50%;
  overflow: auto;
  padding: 16px 32px;
  max-width: 80%;
  max-height: 80%;
  border-radius: 8px;
  background-color: var(--bg-color);
  filter: drop-shadow(0 4px 8px rgba(0, 0, 0, 0.2));
  transform: translate(-50%, -50%);
}

.close-button {
  position: fixed;
  top: 13px;
  right: 13px;
  display: inline-flex;
  width: 32px;
  height: 32px;
  border-radius: 50%;
  color: var(--secondary-color);
  cursor: pointer;
  transition: all 0.2s;
  align-items: center;
  justify-content: center;
}

.close-button:hover {
  color: var(--font-color);
}

input[type="file"] {
  display: none;
}

.theme-switch {
  position: relative;
  display: inline-block;
  width: 32px;
  height: 16px;
}

.theme-switch input {
  display: none;
}

.slider {
  position: absolute;
  top: 0;
  right: 0;
  bottom: 0;
  left: 0;
  border-radius: 8px;
  background-color: rgba(0, 0, 0, 0.1);
  cursor: pointer;
  transition: 0.2s;
}

.slider:hover:before {
  background: rgba(0, 0, 0, 0.2);
}

.slider:active:before {
  background: rgba(0, 0, 0, 0.3);
}

.slider:before {
  position: absolute;
  bottom: 0;
  left: 0;
  width: 16px;
  height: 16px;
  border-radius: 8px;
  background-color: rgba(0, 0, 0, 0.1);
  content: "";
  transition: 0.2s;
}

input:checked + .slider {
  background-color: var(--afont-color);
}

input:checked + .slider:before {
  transform: translateX(16px);
}

.content {
  display: flex;
  overflow: hidden;
  flex-grow: 1;
}

#MathJax_Message {
  display: none;
}

textarea {
  z-index: 0;
  display: flex;
  padding: 16px;
  width: 50vw;
  height: 100%;
  background-color: var(--bg-color);
  color: var(--font-color);
  font-weight: 700;
  font-size: 18px;
  font-family: "Roboto Mono", "SF Mono", "Lucida Console", Monaco, monospace;
  line-height: 2;
  resize: none;
  transition: width 0.2s, padding 0.4s;
  flex-grow: 1;
}

#editor {
  border-right: 2px dashed var(--afont-color);
}

.markdown {
  display: flex;
  flex-direction: column;
  overflow: auto;
  padding: 16px;
  counter-reset: line;
  font-family: "Segoe UI", "Arial", "Roboto", "Noto", sans-serif;
  transition: width 0.2s, padding 0.4s;
  flex-grow: 1;
}

.hljs {
  display: inline-flex !important;
}

pre .hljs {
  display: block !important;
}

h1,
h2,
h3,
h4,
h5,
h6,
p {
  margin: 4px 0;
  counter-increment: line;
}

h1:hover::after,
h2:hover::after,
h3:hover::after,
h4:hover::after,
h5:hover::after,
h6:hover::after,
p:hover::after {
  display: inline-block;
  padding-left: 8px;
  content: "¶" counter(line);
  opacity: 0.5;
}

h1,
h2 {
  border-bottom: 2px solid var(--dbg-color);
}

pre,
code {
  border-radius: 8px;
  font-weight: 700;
  font-size: 18px;
  font-family: "Roboto Mono", "SF Mono", "Lucida Console", Monaco, monospace;
}

blockquote {
  margin-left: 0;
  padding-left: 16px;
  border-left: 2px solid var(--dbg-color);
}

hr {
  width: 100%;
  border: 2px solid var(--dbg-color);
}

table {
  border: 2px solid var(--dbg-color);
  border-spacing: 0;
  border-collapse: separate;
  border-radius: 8px;
}

td,
th {
  padding: 8px 16px;
  border-top: 2px solid var(--dbg-color);
  border-left: 2px solid var(--dbg-color);
  text-align: left;
}

th {
  border-top: none;
}

td:first-child,
th:first-child {
  border-left: none;
}

img {
  max-width: 100%;
}

@media (max-width: 880px) {
  .content {
    flex-direction: column;
  }

  textarea {
    width: 100vw;
    height: calc(50vh - 57px);
  }

  #editor {
    border: 0;
    border-bottom: 2px dashed var(--afont-color);
  }

  .preview {
    display: none;
  }
}