Create style.css

public-html/style.css

@@ -0,0 +1,27 @@
+body {
+    font-family: sans-serif;
+    text-align: center;
+    background: #f0f0f0;
+}
+
+table {
+    margin: 0 auto;
+    border-collapse: collapse;
+}
+
+td {
+    width: 30px;
+    height: 30px;
+    border: 1px solid #999;
+    text-align: center;
+    vertical-align: middle;
+    font-size: 20px;
+}
+
+button {
+    width: 100%;
+    height: 100%;
+    border: none;
+    background: transparent;
+    cursor: pointer;
+}