增加记忆翻牌提示

h5/flipper/flipper.css

@@ -10,6 +10,17 @@
   grid-gap: 1.25%;
   padding: 26.48148148148148% 16.34259259259259% 0 16.34259259259259%;
 }
+.flipper .tip {
+  position: absolute;
+  top: 0;
+  bottom: 0;
+  left: 0;
+  right: 0;
+  margin: auto;
+  background: center / 65.83333333333333% no-repeat url("./tip.png"),
+    rgba(0, 0, 0, 0.6);
+  z-index: 1;
+}
 .flipper .meta {
   position: absolute;
   top: 16.6%;

h5/flipper/game.js

@@ -23,6 +23,14 @@ export default class Game {
     this.init();
   }
   init() {
+    const tip = document.createElement("div");
+    tip.className = "tip";
+    this.cardsContainer.appendChild(tip);
+    tip.addEventListener("click", (e) => {
+      e.stopPropagation();
+      e.preventDefault();
+      this.cardsContainer.removeChild(tip);
+    });
     Object.assign(this, {
       steps: 40,
       score: 0,