整理した

src/client/app/init.css

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+/**
+ * Boot screen style
+ */
+
+@charset 'utf-8';
+
+html {
+	font-family: sans-serif;
+}
+
+body > noscript {
+	position: fixed;
+	z-index: 2;
+	top: 0;
+	left: 0;
+	width: 100%;
+	height: 100%;
+	text-align: center;
+	background: #fff;
+}
+	body > noscript > p {
+		display: block;
+		margin: 32px;
+		font-size: 2em;
+		color: #555;
+	}
+
+#ini {
+	position: fixed;
+	z-index: 1;
+	top: 0;
+	left: 0;
+	width: 100%;
+	height: 100%;
+	text-align: center;
+	background: #fff;
+	cursor: wait;
+}
+	#ini > p {
+		display: block;
+		user-select: none;
+		margin: 32px;
+		font-size: 4em;
+		color: #555;
+	}
+		#ini > p > span {
+			animation: ini 1.4s infinite ease-in-out both;
+		}
+		#ini > p > span:nth-child(1) {
+			animation-delay: 0s;
+		}
+		#ini > p > span:nth-child(2) {
+			animation-delay: 0.16s;
+		}
+		#ini > p > span:nth-child(3) {
+			animation-delay: 0.32s;
+		}
+
+@keyframes ini {
+	0%, 80%, 100% {
+		opacity: 1;
+	}
+	40% {
+		opacity: 0;
+	}
+}