This is the CSS template that I made for my Bear Blog, based on my old Jekyll blog theme. I licensed this under MIT license. Demo: https://felleura.bearblog.dev/desperat-igitur-pastoris/

felleura.css

@import url('https://fonts.googleapis.com/css2?family=DM+Mono:ital,wght@0,300;0,400;0,500;1,300;1,400;1,500&family=Grandstander:ital,wght@0,100..900;1,100..900&family=Open+Sans:ital,wght@0,300..800;1,300..800&display=swap');
:root {
  --brand-color-1: #186cb8;
  --brand-color-2: #2a9a9f;
  --brand-color-3: #f1b211;
  --brand-color-4: #e83611;
  --brand-color-5: #f9002f;
  --brand-green: #2ecc40;
  --brand-yellow: #ffdc00;
  --brand-red: #ff4136;
  --color-navy: #001f3f;
  --color-blue: #0074d9;
  --color-aqua: #7fdbff;
  --color-teal: #39cccc;
  --color-olive: #3d9970;
  --color-green: #2ecc40;
  --color-lime: #01ff70;
  --color-yellow: #ffdc00;
  --color-orange: #ff851b;
  --color-red: #ff4136;
  --color-fuchsia: #f012be;
  --color-purple: #b10dc9;
  --color-maroon: #85144b;
  --color-white: #ffffff;
  --color-silver: #dddddd;
  --color-gray: #aaaaaa;
  --color-black: #111111;
  --link-1: #186cb8;
  --link-2: #186cb8;
  --link-hover-color: #fff;
  --normalize-mark-bg: #ff0;
  --normalize-mark-color: #000;
  --button-bg: #fff;
  --button-border: #333;
  --button-color: #333;
  --button-hover-color: #fff;
  --button-shadow: rgba(0, 0, 0, 0.2);
  --message-color: #717171;
  --message-bg: #f9f9f9;
  --message-border: #ddd;
  --body-color: #414141;
  --body-bg: #fff;
  --body-text-shadow: rgba(0, 0, 0, 0.004);
  --heading-color: #313131;
  --abbr-color: #555;
  --abbr-border: #e5e5e5;
  --blockquote-color: #7a7a7a;
  --blockquote-border: #ddd;
  --blockquote-bg: #f8f8f8;
  --img-shadow: rgba(0, 0, 0, 0.25);
  --tag-color: #999;
  --tag-border: #ddd;
  --tag-hover-border: #555;
  --tag-hover-color: #fff;
  --tag-hover-bg: #444;
  --postdate-color: #888;
  --copyright-color: #888;
  --warning-bg: #f8dc81;
  --warning-color: #414141;
  --hrline-color: #ccc;
  --spacer-border: #ddd;
  --header-border: #ccc;
  --header-bg: #f8f8f8;
  --code-color: #000;
  --code-bg: #eee;
  --footnote-bg: #f3f3f3;
  --table-row-odd-bg: #f9f9f9;
  --table-border: #e5e5e5;
  --figure-bg-1: #dfdfdf;
  --figure-bg-2: #ffffff;
  --figure-img-border: #ddd;
  --figure-img-bg: #fff;
  --figure-caption-bg: #fff;
  --figure-img-shadow: rgba(0, 0, 0, 0.1);
  --postlabel-border: #ddd;
  --postlabel-color: #ccc;
  --pre-bg: #f8f8f8;
  --pre-border: #dddddd;
  --pre-code-color: #008000;
  --pre-line-border: #cccccc;
  --pre-line-color: #cccccc;
}
[data-theme="dark"] {
  --body-bg: #000;
  --body-color: #aaa;
  --body-text-shadow: rgba(255, 255, 255, 0.004);
  --header-border: #333;
  --header-bg: #000;
  --spacer-border: #333;
  --hrline-color: #333;
  --tag-border: #333;
  --link-1: #2a9a9f;
  --link-2: #2a9a9f;
  --link-hover-color: #000;
  --postdate-color: #444;
  --postlabel-border: #333;
  --postlabel-color: #444;
  --button-bg: #111;
  --button-border: #888;
  --button-color: #aaa;
  --button-hover-color: #000;
  --button-shadow: rgba(255, 255, 255, 0.5);
  --heading-color: #bbb;
  --header-bg: #222;
  --code-color: #ccc;
  --code-bg: #333;
  --pre-bg: #222;
  --pre-border: #333;
  --pre-code-color: #008000;
  --pre-line-border: #333;
  --pre-line-color: #333;
  --blockquote-color: #999;
  --blockquote-border: #333;
  --blockquote-bg: #1a1a1a;
  --table-row-odd-bg: #0a0a0a;
  --table-border: #333;
  --figure-bg-1: #333;
  --figure-bg-2: #000;
  --figure-img-border: #444;
  --figure-img-bg: #000;
  --figure-caption-bg: #000;
  --figure-img-shadow: rgba(255, 255, 255, 0.4);
  --footnote-bg: #111;
}
/*! normalize.css v3.0.2 | MIT License | git.io/normalize */
html {
  font-family: sans-serif;
  -ms-text-size-adjust: 100%;
  -webkit-text-size-adjust: 100%;
}
body {
  margin: 0;
}
article,
aside,
details,
figcaption,
figure,
footer,
header,
hgroup,
main,
menu,
nav,
section,
summary {
  display: block;
}
audio,
canvas,
progress,
video {
  display: inline-block;
  vertical-align: baseline;
}
audio:not([controls]) {
  display: none;
  height: 0;
}
[hidden],
template {
  display: none;
}
a {
  background-color: transparent;
}
a:active,
a:hover {
  outline: 0;
}
abbr[title] {
  border-bottom: 1px dotted;
}
b,
strong {
  font-weight: 700;
}
dfn {
  font-style: italic;
}
h1 {
  font-size: 2em;
  margin: 0.67em 0;
}
mark {
  background: var(--normalize-mark-bg);
  color: var(--normalize-mark-color);
}
small {
  font-size: 80%;
}
sub {
  font-size: 75%;
  line-height: 0;
  position: relative;
  vertical-align: baseline;
}
sup {
  font-size: 75%;
  line-height: 0;
  position: relative;
  vertical-align: baseline;
  top: -0.5em;
}
sub {
  bottom: -0.25em;
}
img {
  border: 0;
}
svg:not(:root) {
  overflow: hidden;
}
figure {
  margin: 1em 40px;
}
hr {
  -webkit-box-sizing: content-box;
  box-sizing: content-box;
  height: 0;
}
pre {
  overflow: auto;
}
code,
kbd,
pre,
samp {
  font-family: monospace, monospace;
  font-size: 1em;
}
button,
input,
optgroup,
select,
textarea {
  color: inherit;
  font: inherit;
  margin: 0;
}
button {
  overflow: visible;
  text-transform: none;
}
select {
  text-transform: none;
}
button,
html input[type="button"] {
  -webkit-appearance: button;
  cursor: pointer;
}
input[type="reset"],
input[type="submit"] {
  -webkit-appearance: button;
  cursor: pointer;
}
button[disabled],
html input[disabled] {
  cursor: default;
}
button::-moz-focus-inner {
  border: 0;
  padding: 0;
}
input {
  line-height: normal;
}
input::-moz-focus-inner {
  border: 0;
  padding: 0;
}
input[type="checkbox"],
input[type="radio"] {
  -webkit-box-sizing: border-box;
  box-sizing: border-box;
  padding: 0;
}
input[type="number"]::-webkit-inner-spin-button,
input[type="number"]::-webkit-outer-spin-button {
  height: auto;
}
input[type="search"] {
  -webkit-appearance: textfield;
  -webkit-box-sizing: content-box;
  box-sizing: content-box;
}
input[type="search"]::-webkit-search-cancel-button,
input[type="search"]::-webkit-search-decoration {
  -webkit-appearance: none;
}
fieldset {
  border: 1px solid silver;
  margin: 0 2px;
  padding: 0.35em 0.625em 0.75em;
}
legend {
  border: 0;
  padding: 0;
}
textarea {
  overflow: auto;
}
optgroup {
  font-weight: 700;
}
table {
  border-collapse: collapse;
  border-spacing: 0;
}
td,
th {
  padding: 0;
}
.hidden {
  display: none;
}
/*! Main Layout Styles */
*,
::after,
::before {
  -webkit-box-sizing: border-box;
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}
body,
html {
  margin: 0;
  padding: 0;
  height: 100%;
  color: var(--body-color);
  background-color: var(--body-bg);
  font-family: "Open Sans", sans-serif;
  font-size: 16px;
  line-height: 1.6;
  text-shadow: 1px 1px 1px var(--body-text-shadow);
  text-rendering: optimizeLegibility !important;
  scroll-behavior: smooth;
  -webkit-font-kerning: normal;
  font-kerning: normal;
  -webkit-font-feature-settings: "kern" 1, "liga" 1;
  font-feature-settings: "kern" 1, "liga" 1;
  display: -webkit-box;
  display: -ms-flexbox;
  display: flex;
  -webkit-box-orient: vertical;
  -webkit-box-direction: normal;
  -ms-flex-direction: column;
  flex-direction: column;
}
a {
  color: var(--link-1);
  text-decoration: none;
  -webkit-transition: all 0.5s ease;
  -o-transition: all 0.5s ease;
  transition: all 0.5s ease;
  overflow-wrap: break-word;
  word-wrap: break-word;
  word-break: break-all;
  word-break: break-word;
  -webkit-hyphens: auto;
  -ms-hyphens: auto;
  hyphens: auto;
  border-bottom: 1px solid var(--link-1);
}
a:hover {
  background-image: none;
  background-color: var(--link-1);
  color: var(--link-hover-color);
}
h1,
h2,
h3,
h4,
h5,
h6 {
  margin: 1rem 0 1rem 0;
  line-height: 1.25;
  color: var(--heading-color);
  text-align: left;
  font-weight: 700;
}
h1 {
  font-size: 2rem;
  font-family: "Grandstander", cursive;
}
h2 {
  font-size: 1.5rem;
  font-family: "Grandstander", cursive;
}
h3 {
  font-size: 1.25rem;
  font-family: "Grandstander", cursive;
}
h4,
h5,
h6 {
  font-size: 1.1rem;
  font-family: "Grandstander", cursive;
}
dt {
  font-weight: 700;
}
dd {
  margin-bottom: 0.5rem;
}
hr {
  position: relative;
  border: 0;
  border-top: 1px solid var(--hrline-color);
  margin: 1.5rem 0;
}
abbr {
  font-weight: 700;
  color: var(--abbr-color);
  text-transform: uppercase;
}
abbr[title] {
  cursor: help;
  border-bottom: 1px dotted var(--abbr-border);
}
code,
pre {
  font-family: "DM Mono", monospace;
  -webkit-font-variant-ligatures: none;
  font-variant-ligatures: none;
  -webkit-font-feature-settings: "liga" 0;
  font-feature-settings: "liga" 0;
}
code {
  background: var(--code-bg);
  color: var(--code-color);
}
pre {
  width: 100%;
  margin: 0 0 1rem 0;
  line-height: 1.4;
  white-space: pre;
  overflow: auto;
  padding: 0.5rem 2rem 0.5rem 0.5rem;
  font-size: 0.9rem;
}
pre code {
  padding: 0;
}
pre .line-number {
  float: left;
  margin: 0 1em 0 -1em;
  -webkit-user-select: none;
  -moz-user-select: none;
  -ms-user-select: none;
  user-select: none;
  text-align: right;
}
pre .line-number span {
  display: block;
  padding: 0 0.5em 0 1em;
}
pre .cl {
  display: block;
  clear: both;
}
blockquote {
  color: var(--blockquote-color);
  border-left: 0.25rem solid var(--blockquote-border);
  margin: 0.8rem 0;
  padding: 0.5rem 1rem;
  background: var(--blockquote-bg);
}
blockquote p:last-child {
  margin-bottom: 0;
}
img {
  display: block;
  border-radius: 3px;
  margin: 1rem 0;
  max-width: 100%;
  height: auto;
  -webkit-box-shadow: 0 1px 3px var(--img-shadow);
  box-shadow: 0 1px 3px var(--img-shadow);
}
figure {
  padding: 1rem 0;
  margin: 0 0 1rem 0;
  background: -o-repeating-linear-gradient(
      315deg,
      var(--figure-bg-1) 0,
      var(--figure-bg-1) 1%,
      var(--figure-bg-2) 0,
      var(--figure-bg-2) 50%
    )
    0/20px 20px;
  background: repeating-linear-gradient(
      135deg,
      var(--figure-bg-1) 0,
      var(--figure-bg-1) 1%,
      var(--figure-bg-2) 0,
      var(--figure-bg-2) 50%
    )
    0/20px 20px;
}
figure img {
  margin: 0 0 0.2rem 0;
  border: 1px solid var(--figure-img-border);
  background-color: var(--figure-caption-bg);
}
figure figcaption {
  font-size: 0.9rem;
  line-height: 1.6;
  font-family: Roboto, -apple-system, Helvetica, Arial, sans-serif;
}
figure figcaption span {
  background-color: var(--figure-caption-bg);
}
figure figcaption a:hover {
  cursor: pointer;
}
table {
  margin-bottom: 1rem;
  width: 100%;
  border: 1px solid var(--table-border);
  border-collapse: collapse;
}
table td a {
  word-break: keep-all;
}
td,
th {
  border: 1px solid var(--table-border);
  padding: 0.25rem 0.5rem;
}
tbody tr:nth-child(odd) td,
tbody tr:nth-child(odd) th {
  background-color: var(--table-row-odd-bg);
}
dl,
ol,
ul {
  margin-left: 1rem;
}
dl li:last-child,
ol li:last-child,
ul li:last-child {
  margin-bottom: 1rem;
}
p {
  margin-bottom: 1rem;
}
a.title {
  text-decoration: none;
  border-bottom: none;
  margin: 0 auto;
}
a.title:hover {
  background: none;
}
a.title h1 {
  font-weight: 900;
  width: fit-content;
  background: -o-linear-gradient(
    231deg,
    var(--brand-color-1) 19%,
    transparent 19%,
    transparent 20%,
    var(--brand-color-2) 20%,
    var(--brand-color-2) 39%,
    transparent 39%,
    transparent 40%,
    var(--brand-color-3) 40%,
    var(--brand-color-3) 59%,
    transparent 59%,
    transparent 60%,
    var(--brand-color-4) 60%,
    var(--brand-color-4) 79%,
    transparent 79%,
    transparent 80%,
    var(--brand-color-5) 80%
  );
  background: linear-gradient(
    219deg,
    var(--brand-color-1) 19%,
    transparent 19%,
    transparent 20%,
    var(--brand-color-2) 20%,
    var(--brand-color-2) 39%,
    transparent 39%,
    transparent 40%,
    var(--brand-color-3) 40%,
    var(--brand-color-3) 59%,
    transparent 59%,
    transparent 60%,
    var(--brand-color-4) 60%,
    var(--brand-color-4) 79%,
    transparent 79%,
    transparent 80%,
    var(--brand-color-5) 80%
  );
  background-clip: text;
  -webkit-background-clip: text;
  color: transparent;
}
a.title h1:hover {
  color: var(--link-1);
}
header {
  display: flex;
  padding: 1rem 2rem;
  flex-direction: column;
  width: 100%;
  margin: 0 auto;
  border-bottom: 1px solid var(--button-border);
}
nav {
  margin: 0 auto;
  padding: 0;
}
nav p {
  display: flex;
  flex-direction: row;
  gap: 1ch;
}
nav a {
  padding: 0 12px;
  white-space: nowrap;
  font-family: "Grandstander", cursive;
  border-bottom: none;
  border-radius: 5px;
}
nav a:hover {
  color: var(--button-hover-color);
}
main {
  background-color: var(--body-bg);
  margin: 0 auto;
  padding: 1rem 2rem;
  display: flex;
  flex-direction: column;
  max-width: 960px;
  width: 100%;
}
footer {
  margin: 0 auto 1rem auto;
  display: flex;
  flex-direction: column;
  font-size: 0.8rem;
  border-top: 1px solid var(--button-border);
  color: var(--copyright-color);
  width: 100%;
  text-align: center;
}
footer a {
  border: none;
}
pre {
  background-color: var(--pre-bg);
  border: 1px solid var(--pre-border);
}
pre code {
  color: var(--pre-code-color);
  background-color: transparent;
}
ul.blog-posts li {
  display: flex;
  flex-direction: row;
}
ul.blog-posts li:last-child {
  margin-bottom: 0;
}
ul.blog-posts li a {
  border-bottom: none;
}
time {
  font-family: "DM Mono", monospace;
  width: fit-content;
  word-wrap: none;
  white-space: nowrap;
  margin-right: 1rem;
  font-style: normal;
  font-size: 0.8em;
  text-transform: uppercase;
}