Reshuffle to put "HTML" (JSX) and CSS together as a theme with logic elsewhere.

themes/base/css/molecules/RoomTile.css

@@ -0,0 +1,36 @@
+.mx_RoomTile {
+    height: 20px;
+    background-color: #ddd;
+    margin-top: 1px;
+    margin-bottom: 1px;
+    padding: 5px;
+    cursor: pointer;
+    border: 2px solid white;
+    transition: background-color 0.1s ease;
+}
+
+.mx_RoomTile.selected {
+    border: 2px inset #eee;
+}
+
+.mx_RoomTile_name {
+    font-size: 80%;
+    font-weight: bold;
+}
+
+.mx_RoomTile div {
+    overflow: hidden;
+    text-overflow: ellipsis;
+}
+
+.mx_RoomTile.unread {
+    background-color: #66e;
+}
+
+.mx_RoomTile.invited {
+    background-color: #6e6;
+}
+
+.mx_RoomTile:hover {
+    background-color: #ff8;
+}