Update default theme.

data/themes/default.css

+.keyboard {
+    background-color: rgba(0, 0, 0, 255);
+    color: #ffffff;
+    font-family: cantarell, sans-serif;
+}
+
 .key {
     color: #ffffff;
     background-gradient-direction: vertical;
-    background-gradient-start: #000000;
-    background-gradient-end: #555555;
+    background-gradient-start: rgba(0, 0, 0, 255);
+    background-gradient-end: rgba(64, 64, 64, 255);
     border-width: 2px;
-    border-color: #777777;
+    border-color: rgba(128, 128, 128, 255);
     border-radius: 3px;
 }
 
 .key:active {
     background-gradient-direction: vertical;
-    background-gradient-start: #FF0000;
-    background-gradient-end: #FF0000;
+    background-gradient-start: rgba(0, 0, 255, 255);
+    background-gradient-end: rgba(64, 64, 255, 255);
+    border-color: rgba(160, 160, 255, 255);
 }
-
-.keyboard {
-    background-color: #000000;
-    color: #ffffff;
-}
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