Update.

res/dungeon/theme.css

-
-* {
-    background: #25131A;
-}
-
-grid.start {
-    background: #25131A;
-}
-
-container {
-    background: #25131A;
-}
-
-container.menu {
-    background: #6E4A48;
-    border-color: #472B43;
-    border-radius: 2;
-    border-width: 2;
-}
-
-button {
-    border-radius: 2;
-    border-width: 4;
-    border-color: #3D253B;
-    background: #895A45;
-    color: #FFFFFF;
-}
-
-button:active {
-    background: #724736;
-}
-
-textblock.h1 {
-    font-size: 24;
-}
\ No newline at end of file