use _ENV to get rid of level_events and spawns

updatedshmup.p8

@@ -887,7 +887,9 @@ function level_frame()
    else
     while cbs do
      assert(cbs[1] == distance)
-     level_events[cbs[2]](unpack(cbs, 3))
+     local f = _ENV[cbs[2]]
+     assert(type(f) == "function", cbs[2].." at "..distance..." is not a function")
+     f(unpack(cbs, 3))
      cbs=cbs.next
     end
    end
@@ -1004,17 +1006,9 @@ function spawn_blocking_boss_chasey()
  return c
 end
 
-spawns = {
- chasey = chasey,
- frownie = frownie,
- blocky = blocky,
- spewy = spewy,
- spewy_xl=spewy_xl,
- -- TODO: populate this
-}
 function std_spawn(tnm, n, blocking, goodie,altspr)
- local typ = spawns[tnm]
- assert(typ, tostr(tnm).." not a spawnable")
+ local typ = _ENV[tnm]
+ assert(typ and typ.new, tostr(tnm).." not a class")
  for i=1,(n or 1) do
   spawn_rnd(typ, blocking, goodie,altspr)
  end
@@ -1047,14 +1041,9 @@ function spawn_goodie(goodie_name, x, y, sz)
  goodies[goodie_name].new{}:spawn_at(x+sh,y+sh)
 end
 
--- TODO: populate level_events
-
--- to implement: multi(times, interval, f, ...)
--- once on this frame, then times-1 times after that spaced interval
--- frames apart, f(...). schedule this like the one-off written in
--- example_level.
 function multi(times, interval, fnm, ...)
- local f,irm = level_events[fnm],interval
+ local f,irm = _ENV[fnm],interval
+ assert(type(f) == "function", fnm.." not a function")
  fnm(...)
  events:push_back{move=function()
   irm-=1