update readability, mermaid styling

layouts/default.html

@@ -6,6 +6,7 @@
     :root {
       --red1: #a20000;
       --red2: #c20000;
+      --red3: #dd4444;
       --dark1: #071213;
       --dark2: #000000;
       --bright1: #aed3d4;
@@ -14,11 +15,12 @@
 
     body {
       background-color: var(--dark2);
-      color: var(--red2);
+      color: var(--red3);
       font-family: monospace;
       font-size: 1.012rem;
       margin: 0;
       padding: 0;
+      line-height: 1.4;
     }
 
     main {
@@ -58,6 +60,13 @@
       overflow-x: scroll;
       tab-size: 2;
     }
+
+    .mermaid {
+      width: fit-content;
+      color: var(--middle1);
+      border: 1px solid var(--red1);
+      padding: 0.5ch 0.5em;
+    }
   </style>
   %%HEAD%%
 </head>