Keep the gradient only on the Simon board

On my screen, white on light isn't great, and I don't think wire colour
indicators really benefit from the gradient.

index.html

@@ -74,10 +74,10 @@
 
             <div id="simonBoard">
                 <div class="simonRow">
-                    <div class="blue">&nbsp;</div><div class="yellow">&nbsp;</div>
+                    <div class="simonBlue">&nbsp;</div><div class="simonYellow">&nbsp;</div>
                 </div>
                 <div class="simonRow">
-                    <div class="red">&nbsp;</div><div class="green">&nbsp;</div>
+                    <div class="simonRed">&nbsp;</div><div class="simonGreen">&nbsp;</div>
                 </div>
                 <div class="arrow" id="arrowRB"></div>
                 <div class="arrow" id="arrowBR"></div>

ktane.css

@@ -26,19 +26,19 @@ button {
     padding: 0.2em;
 }
 .red {
-    background: radial-gradient(#fb9a9a,#fc7373,red);
+    background-color: red;
     color: white;
 }
 .yellow {
-    background: radial-gradient(#fbfb9a,#fcfc73,yellow);
+    background-color: yellow;
     color: black;
 }
 .blue {
-    background: radial-gradient(#9a9afb,#7373fc,blue);
+    background-color: blue;
     color: white;
 }
 .green {
-    background: radial-gradient(#98c998,#72b772,green);
+    background-color: green;
     color: white;
 }
 .white {
@@ -47,7 +47,7 @@ button {
     color: black;
 }
 .black {
-    background: radial-gradient(#969696,#757575,black);
+    background-color: black;
     color: white;
 }
 .button.white {
@@ -147,6 +147,18 @@ h2 {
 #simonBoard > .simonRow > div:last-child {
     border-right-width: 4px;
 }
+.simonRed {
+    background: radial-gradient(#fb9a9a, #fc7373, red);
+}
+.simonYellow {
+    background: radial-gradient(#fbfb9a, #fcfc73, yellow);
+}
+.simonBlue {
+    background: radial-gradient(#9a9afb, #7373fc, blue);
+}
+.simonGreen {
+    background: radial-gradient(#98c998, #72b772, green);
+}
 
 .arrow {
     background-color: black;