more efficient bullet spawning

vacuum_gambit.p8

@@ -618,14 +618,6 @@ end
 -->8
 -- bullet and gun behaviors
 
-function player_blt_cat()
- return pbullets
-end
-
-function enemy_blt_cat()
- return ebullets
-end
-
 -- x, y: position
 -- dx, dy: movement (linear)
 -- f: frames remaining; nil for no limit
@@ -638,9 +630,9 @@ end
 --   details, check impl
 -- damage -- damage to do to
 --   a ship that gets hit
--- category -- function that
---   returns which bullet list
---   to spawn onto
+-- category -- string naming
+--   which bullet list to spawn
+--   onto, from _ENV
 -- hitship -- event handler,
 --   takes ship as argument.
 --   default: die, return true.
@@ -785,7 +777,7 @@ end
 function bullet_base:spawn_at(x, y)
  self.x = x - self.x_off
  self.y = y - self.y_off
- add(self.category(), self)
+ add(_ENV[self.category], self)
 end
 
 function gun_base:shoot(x, y)
@@ -855,7 +847,7 @@ zap_p = mknew(bullet_base.new{
 
  hitship = const_fxn(true),
 
- category = player_blt_cat,
+ category = "pbullets",
 })
 
 zap_gun_p = mknew(gun_base.new{
@@ -914,7 +906,7 @@ blast = mknew(bullet_base.new{
    end)
   end
  end,
- category=player_blt_cat
+ category="pbullets"
 })
 
 blast_gun = mknew(gun_base.new{
@@ -953,14 +945,14 @@ protron_e = mknew(bullet_base.new{
  y_off = 4,
  
  damage = 1,
- category = enemy_blt_cat,
+ category = "ebullets",
 })
 
 protron_p = mknew(protron_e.new{
  sprite=23,
  dym = -1,
  y_off = 0,
- category=player_blt_cat,
+ category="pbullets",
 })
 
 protron_gun_e = mknew(gun_base.new{
@@ -1007,13 +999,13 @@ vulcan_e = mknew(bullet_base.new{
  y_off = 0,
  
  damage = 0.5,
- category=enemy_blt_cat
+ category="ebullets"
 })
 
 vulcan_p = mknew(vulcan_e.new{
  sprite=22,
  y_off = 4,
- category=player_blt_cat
+ category="pbullets"
 })
 
 vulcan_gun_e = mknew(gun_base.new{
@@ -1656,7 +1648,7 @@ xp_gem = mknew(bullet_base.new{
  dy = 0.75,
  width=1, -- not used for spr but
  height=1,-- bullet_base uses it
- category = enemy_blt_cat,
+ category = "ebullets",
  damage = 0,
  hurt = {
   x_off = -2,