Use CSS vars

public/styles/style.css

@@ -1,5 +1,13 @@
 /* @import url('https://fonts.googleapis.com/css2?family=Source+Code+Pro&display=swap'); */
 
+:root {
+    --fp-primary: #0F0;
+    --fp-background: #000;
+    --fp-secondary: #0FF;
+    --fp-danger: #F00;
+    --fp-dim: #111;
+}
+
 @font-face {
     font-family: 'Source Code Pro';
     src: url('/fonts/SourceCodePro.ttf');
@@ -8,24 +16,24 @@
 * {
     color-scheme: light dark;
     font-family: 'Source Code Pro', monospace !important;
-    color: #0F0;
+    color: var(--fp-primary);
 }
 
 html, body {
     height: 100%;
     width: 100%;
-    color: #0F0;
+    color: var(--fp-primary);
     margin: 0;
     padding: 0;
     font-family: 'Source Code Pro', monospace !important;
 }
 
 html {
-    background-color: #000;
+    background-color: var(--fp-background);
 }
 
 .warning {
-    color: #F00;
+    color: var(--fp-danger);
 }
 
 body {
@@ -52,7 +60,7 @@ a:has(button) {
     box-shadow: none;
     transform: none;
     outline: none;
-    background: #000;
+    background: var(--fp-background);
 }
 
 .center {
@@ -69,16 +77,6 @@ a:has(button) {
     text-align: right;
 }
 
-/*
-.rainbow {
-    background: linear-gradient(90.02deg, #F00 0.02%, #E0F 27.09%, #0BF 51.04%, #0F1 76.56%, #F00 99.99%);
-    -webkit-background-clip: text;
-    -webkit-text-fill-color: transparent;
-    background-clip: text;
-    text-fill-color: transparent;
-}
-*/
-
 .rainbow {
     background: linear-gradient(to right, #F00 0%, #E0F 10%, #0BF 30%, #0F1 50%, #F00 90%);
     -webkit-background-clip: text;
@@ -88,11 +86,11 @@ a:has(button) {
 }
 
 .color {
-    color: #0F0;
+    color: var(--fp-primary);
 }
 
 .force-color {
-    background: #0F0;
+    background: var(--fp-primary);
     -webkit-background-clip: text;
     -webkit-text-fill-color: transparent;
     background-clip: text;
@@ -107,7 +105,7 @@ a:has(button) {
 }
 
 pre {
-    background: #111;
+    background: var(--fp-dim);
     width: 100%;
     max-width: 100%;
     min-width: 100%;
@@ -115,7 +113,6 @@ pre {
 
 code {
     overflow-x: auto;
-    max-width: 100%;
     display: block;
     margin: 0ch 1ch;
 }