Attempt to center things a little

www/game.css

@@ -27,7 +27,6 @@
   border: 1px solid #555;
   width: 4.5em;
   height: 7em;
-  max-height: 10%;
   float: left;
   margin: 0.5em;
 }
@@ -114,13 +113,26 @@
 
 #game ul {
   display: inline-block;
-  margin-left: 3em;
+  margin: 0 0 0 3.5em;
   padding: 0;
   float: right;
+  position: relative;
+  top: 50%;
+  transform: translateY(-50%);
+}
+
+#game ul#river {
+  position: absolute;
+  left: 50%;
+  transform: translate(-50%, -50%);
+  margin-left: 0;
+  display: flex;
+  flex-wrap: wrap;
+  justify-content: center;
 }
 
 #them .card, #you .card {
-  margin-left: -3em;
+  margin-left: -3.5em;
 }
 
 #game #you .hand {
@@ -129,5 +141,5 @@
 }
 
 #you .hand .card {
-  margin-left: 0.5em;
+  margin: 0.5em 0.1em;
 }