scroll tech when choosing tech

you can scroll through the tech and gun menus while selecting power ups
added another classic n-gon option in settings

tech: options exchange - canceling tech,gun,field has a 90% chance for a reroll

stabber mobs now stab 15% shorter distance, but they can stab more often
weak interaction gives 5->10 max energy per unused power up

bug fixes

style.css

@@ -171,7 +171,7 @@ summary {
 
 #choose-background {
     position: absolute;
-    z-index: 3;
+    z-index: 2;
     width: 100%;
     height: 100%;
     background-color: #ccc;