[S] Style overlay

AquaNet/src/app.sass

@@ -37,7 +37,12 @@ h1
 
 
 .card
-  padding: 2em
+  display: flex
+  flex-direction: column
+
+  border-radius: 5px
+  padding: 12px 16px
+  background: $ov-light
 
 
 #app
@@ -141,4 +146,33 @@ main.content
 
   @media (max-width: $w-mobile)
     margin: 100px 0 0
-    padding: 0 32px 16px
+    padding: 0 32px 16px
+
+
+// Overlay
+.overlay
+  position: fixed
+  inset: 0
+
+  background-color: rgba(0, 0, 0, 0.5)
+
+  display: flex
+  justify-content: center
+  align-items: center
+
+  z-index: 1000
+
+  h2, p
+    user-select: none
+    margin: 0
+
+  > div
+    background-color: $c-bg
+    padding: 2rem
+    border-radius: 10px
+
+    display: flex
+    flex-direction: column
+    gap: 1rem
+
+    max-width: 400px