tabi: add sysret skin

themes/tabi-lean/sass/skins/sysret.scss

@@ -0,0 +1,40 @@
+/* general */
+
+
+/* theme */
+@mixin theme-variables($theme) {
+  @if $theme =='light' {
+      --primary-color: #F5F5F5;
+      --background-color: #0D0D0D;
+  }
+  @else if $theme == 'dark' {
+    --primary-color: #F5F5F5;
+    --background-color: #0D0D0D;
+  }
+}
+
+:root {
+    @include theme-variables('light');
+}
+
+[data-theme='dark'] {
+    @include theme-variables('dark');
+}
+
+@media (prefers-color-scheme: dark) {
+    :root:not([data-theme='light']) {
+        @include theme-variables('dark');
+    }
+}
+
+
+/* header */
+.home-title {
+    background-color: var(--primary-color);
+    color: var(--background-color);
+    padding: 0.12rem;
+}
+
+.nav-links {
+    text-decoration: underline;
+}