seeded random

all runs are now seeded
seed defaults to the last 8 digits of UTC time in milliseconds
set a custom randomization seed in settings
seed controls:
    at start - boss list, mob type list, level list, horizontal flip
    during run - tech, gun, field choices, some custom level randomization
doesn't control: mob spawns, mob size, some minor level differences, specific level boss choices, ammo reward values, specific tech effects

bug fix with ground state

index.html

@@ -90,6 +90,11 @@
             <details>
                 <summary>settings</summary>
                 <div style="line-height: 150%;" class="details-div">
+
+                    <label for="seed">randomization seed:</label>
+                    <input type="text" id="seed" name="seed" autocomplete="off" spellcheck="false" minlength="1" size="20" style="width: 120px;">
+                    <br>
+
                     <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" style="background-color: #fff">
                         <option value="1">easy</option>