Another super feature: auto dark mode!

assets/css/_dark/dark-main.scss

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+/*!
+* The main dark mode styles
+* v2.0
+* https://github.com/cotes2020/jekyll-theme-chirpy
+* © 2018-2019 Cotes Chung
+* MIT Licensed
+*/
+
+@media (prefers-color-scheme: dark) {
+  html {
+    /* framework */
+    --main-wrapper-bg: rgb(27, 27, 30);
+    --topbar-wrapper-bg: rgb(39, 40, 43);
+    --search-wrapper-bg: rgb(34, 34, 39);
+    --search-icon: rgb(100, 102, 105);
+    --input-focus-border: rgb(112, 114, 115);
+    --footer-bg: rgb(31, 30, 30);
+    --footer-border: rgb(44, 45, 45);
+    --mask-bg: rgb(68, 69, 70);
+
+    /* sidebar */
+    --nav-cursor: rgb(183, 182, 182);
+    --sidebar-bg: radial-gradient(circle, #231c4c 0%, #1d1f27 100%);
+
+    /* common color */
+    --text-color: rgb(175, 176, 177);
+    --link-color: rgb(138, 180, 248);
+    --main-border: rgb(63, 65, 68);
+    --button-bg: rgb(39, 40, 33);
+    --blockquote-border: rgb(93, 95, 82);
+    --blockquote-text: rgb(96, 125, 139);
+
+    --card-bg: rgb(39, 40, 33);
+    --card-header-bg: rgb(51, 50, 50);
+    --relate-post-title: rgb(164, 175, 181);
+
+    /* posts */
+    --toc-highlight: rgb(116, 178, 243);
+    --tag-bg: rgb(41, 40, 40);
+    --tag-hover: rgb(43, 56, 62);
+    --tb-odd-bg: rgb(50, 51, 41); /* posts' table odd line */
+
+    /* tags */
+    --tag-border: rgb(59, 79, 88);
+    --tag-shadow: rgb(32, 33, 33);
+
+    /* categories */
+    --categories-hover-bg: rgb(73, 75, 76);
+
+    /* archives */
+    --timeline-node-bg: rgb(150, 152, 156);
+  }
+}

assets/css/_dark/dark-syntax.scss

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+/*!
+* The syntax dark mode styles
+* v2.0
+* https://github.com/cotes2020/jekyll-theme-chirpy
+* © 2018-2019 Cotes Chung
+* MIT Licensed
+*/
+
+@media (prefers-color-scheme: dark) {
+  html {
+    /* syntax highlight colors from https://raw.githubusercontent.com/jwarby/pygments-css/master/monokai.css */
+    --highlight-pre-bg: #272822;
+    --highlight-hll-bg: #272822;
+    --highlight-c: #75715e; /* Comment */
+    --highlight-err: #960050; /* Error */
+    --highlight-err-bg: #1e0010; /* Error background */
+    --highlight-k: #66d9ef; /* Keyword */
+    --highlight-l: #ae81ff; /* Literal */
+    --highlight-n: #f8f8f2; /* Name */
+    --highlight-o: #f92672; /* Operator */
+    --highlight-p: #f8f8f2; /* Punctuation */
+    --highlight-cm: #75715e; /* Comment.Multiline */
+    --highlight-cp: #75715e; /* Comment.Preproc */
+    --highlight-c1: #75715e; /* Comment.Single */
+    --highlight-cs: #75715e; /* Comment.Special */
+    --highlight-kc: #66d9ef; /* Keyword.Constant */
+    --highlight-kd: #66d9ef; /* Keyword.Declaration */
+    --highlight-kn: #f92672; /* Keyword.Namespace */
+    --highlight-kp: #66d9ef; /* Keyword.Pseudo */
+    --highlight-kr: #66d9ef; /* Keyword.Reserved */
+    --highlight-kt: #66d9ef; /* Keyword.Type */
+    --highlight-ld: #e6db74; /* Literal.Date */
+    --highlight-m: #ae81ff; /* Literal.Number */
+    --highlight-s: #e6db74; /* Literal.String */
+    --highlight-na: #a6e22e; /* Name.Attribute */
+    --highlight-nb: #f8f8f2; /* Name.Builtin */
+    --highlight-nc: #a6e22e; /* Name.Class */
+    --highlight-no: #66d9ef; /* Name.Constant */
+    --highlight-nd: #a6e22e; /* Name.Decorator */
+    --highlight-ni: #f8f8f2; /* Name.Entity */
+    --highlight-ne: #a6e22e; /* Name.Exception */
+    --highlight-nf: #a6e22e; /* Name.Function */
+    --highlight-nl: #f8f8f2; /* Name.Label */
+    --highlight-nn: #f8f8f2; /* Name.Namespace */
+    --highlight-nx: #a6e22e; /* Name.Other */
+    --highlight-py: #f8f8f2; /* Name.Property */
+    --highlight-nt: #f92672; /* Name.Tag */
+    --highlight-nv: #f8f8f2; /* Name.Variable */
+    --highlight-ow: #f92672; /* Operator.Word */
+    --highlight-w: #f8f8f2; /* Text.Whitespace */
+    --highlight-mf: #ae81ff; /* Literal.Number.Float */
+    --highlight-mh: #ae81ff; /* Literal.Number.Hex */
+    --highlight-mi: #ae81ff; /* Literal.Number.Integer */
+    --highlight-mo: #ae81ff; /* Literal.Number.Oct */
+    --highlight-sb: #e6db74; /* Literal.String.Backtick */
+    --highlight-sc: #e6db74; /* Literal.String.Char */
+    --highlight-sd: #e6db74; /* Literal.String.Doc */
+    --highlight-s2: #e6db74; /* Literal.String.Double */
+    --highlight-se: #ae81ff; /* Literal.String.Escape */
+    --highlight-sh: #e6db74; /* Literal.String.Heredoc */
+    --highlight-si: #e6db74; /* Literal.String.Interpol */
+    --highlight-sx: #e6db74; /* Literal.String.Other */
+    --highlight-sr: #e6db74; /* Literal.String.Regex */
+    --highlight-s1: #e6db74; /* Literal.String.Single */
+    --highlight-ss: #e6db74; /* Literal.String.Symbol */
+    --highlight-bp: #f8f8f2; /* Name.Builtin.Pseudo */
+    --highlight-vc: #f8f8f2; /* Name.Variable.Class */
+    --highlight-vg: #f8f8f2; /* Name.Variable.Global */
+    --highlight-vi: #f8f8f2; /* Name.Variable.Instance */
+    --highlight-il: #ae81ff; /* Literal.Number.Integer.Long */
+
+    // --highlight-gh: none; /* Generic Heading & Diff Header */
+    --highlight-gu: #75715e; /* Generic.Subheading & Diff Unified/Comment? */
+    --highlight-gd: #f92672; /* Generic.Deleted & Diff Deleted */
+
+    /* My styles */
+    --highlight-lineno: #6c6c6d;
+    --highlight-lineno-border: #3c4042;
+  }
+
+  pre {
+    color: #818c96; /* override Bootstrap */
+  }
+
+}