Assorted micro-optimizations.

Some of these are pure token optimizations, some spend tokens for performance. Function calls are particularly expensive in Pico-8, so using the table form of `pal` whenever changing multiple colors seems worth it.

Also fixes a bug in palette swapping.

chameleonic.p8

@@ -101,19 +101,13 @@ function _apply(x,ts,a)
 end
 
 function sgn0(x)
-	if (x==0) return x
+ if (x==0) return x
-	return sgn(x)
+ return sgn(x)
 end
 
 function _mnmx(x,y)
- return min(x,y),max(x,y)
+ if (x>y)return y,x
-end
+ return x,y
--->8
-bg={}
-add(modules,bg)
-
-function bg:draw0()
- cls(0)
 end
 -->8
 level={}
@@ -139,6 +133,7 @@ function level:advance()
  self:reinit(self.ix+1)
 end
 
+pitpal = {[0]=1, [7]=0}
 function level:draw()
  cls(1)
  pal(1,0)
@@ -150,11 +145,11 @@ function level:draw()
  for _,pit in pairs(self._pits) do
   spr(pit.s,pit.px,pit.py)
   if pit.contents then
-   pal(7,0)
+   pal(pitpal)
-   pal(0,1)
    palt(0,false)
    spr(pit.contents,pit.px,pit.py)
    pal()
+   pal(1,0)
  end
  for _,crate in pairs(self._crates) do
   spr(crate.s,crate.px,crate.py)
@@ -179,7 +174,7 @@ function level:update()
 
   if #crate.todo==0 then 
    local pit=self._pits[_mix(crate.mx,crate.my)]
-   if pit!=nil and pit.contents==nil then
+   if pit and not pit.contents then
     add(remove,cix)
     crate.dead=true
     pit.contents=crate.s
@@ -205,7 +200,7 @@ function level:load_dynobjs()
    local px,py=mx*8,my*8
    local s=self:_mget(mx,my)
    local def=self:_get_cratedef(s)
-   if def!=nil then
+   if def then
     self._crates[mxy]={
      s=s,def=def,
      mx=mx,my=my,
@@ -228,8 +223,8 @@ end
 
 function level:recollide()
  self._coll={}
- for mx=0,15,1 do
+ for mx=0,15 do
-  for my=0,15,1 do
+  for my=0,15 do
    local mxy=_mix(mx,my)
    self._coll[mxy]=
     fget(self:_mget(mx,my),7) or
@@ -239,16 +234,16 @@ function level:recollide()
 end
 
 function level:reanchor(remove)
- if remove or self._anch==nil then
+ if remove or not self._anch then
   self._anch={}
  end
 
- for ax0=0,31,1 do
+ for ax0=0,31 do
-  for ay0=0,31,1 do
+  local ax1 = ax0-1+2*(ax0%2)
-   local ax1,ay1=ax0-1+2*(ax0%2),ay0-1+2*(ay0%2)
+  local mx0,mx1 = ax0\2,ax1\2
-
+  for ay0=0,31 do
-   local mx0,my0=ax0\2,ay0\2
+   local ay1=ay0-1+2*(ay0%2)
-   local mx1,my1=ax1\2,ay1\2
+   local my0,my1=ay0\2,ay1\2
 
    if (
     not self:mcoll(mx0,my0) and