Update crafting page checks to fade in

Update the crafting page so that the check mark for each step only
appears when hovering over that step, and so that the check also has
some descriptive text helping the user understand what it does.

src/scss/main.scss

@@ -62,6 +62,11 @@ $color-brick-light:        #D9D9D9;
 $color-dirt:               #906647;
 $color-ice:                #8AA7E6;
 
+// Opacity Values //////////////////////////////////////////////////////////////////////////////////
+
+$opacity-hidden: 0.000001;
+$opacity-shown:  1.0;
+
 // Style Colors ////////////////////////////////////////////////////////////////////////////////////
 
 $color-active:             #5C8AE6;
@@ -69,6 +74,7 @@ $color-active-hover:       #2E6BE6;
 $color-background:         #AAC9FF;
 $color-background-panel:   #FFFFFF;
 $color-background-toolbar: rgba(255, 255, 255, 0.75);
+$color-checkmark:          #7EDD7B;
 $color-content:            rgba(230, 230, 230, 0.90);
 $color-error:              #F3C2C2;
 $color-error-new:          #CD0000;