minor fixes on opacities and color

site/src/routes/tutorial/[slug]/_TableOfContents.svelte

@@ -30,13 +30,17 @@
 		display: block;
 		padding: 0.7em 0;
 		text-align: center;
-		opacity: 0.7;
+		opacity: 0.75;
 		color: white;
 	}
 
+	a:hover {
+		opacity: 1;
+	}
+
 	a.disabled, a.disabled:hover, a.disabled:active {
 		color: white;
-		opacity: 0.4;
+		opacity: 0.3;
 	}
 
 	span {

site/src/routes/tutorial/[slug]/index.svelte

@@ -166,7 +166,7 @@
 		font-size: var(--h3);
 		line-height: 1;
 		font-weight: 400;
-		color: var(--sidebar-text);
+		color: white;
 	}
 
 	.chapter-markup :global(h2:first-child) {
@@ -213,7 +213,7 @@
 	}
 
 	.controls {
-		border-top: 1px solid rgba(0,0,0,.25);
+		border-top: 1px solid rgba(255,255,255,.15);
 		padding: 1em 0 0 0;
 		display: flex;
 	}