only 3 bosses

several tech now have fewer requirements to unlock
some normal tech is now considered gun tech (mostly explosion stuff)
snakeBoss tails, stay attached to each other
"snakeBoss", "blockBoss", "powerupBoss" are now the only bosses for the random boss list

bug fixes

index.html

@@ -99,7 +99,7 @@
                 <summary>settings</summary>
                 <div style="line-height: 150%;" class="details-div">
                     <label for="difficulty-select" title="effects: number of mobs, damage done by mobs, damage done to mobs, mob speed, heal effects">combat difficulty:</label>
-                    <select name="difficulty-select" id="difficulty-select">
+                    <select name="difficulty-select" id="difficulty-select" style="background-color: #fff">
                         <option value="1">easy</option>
                         <option value="2" selected>normal</option>
                         <option value="4">hard</option>