diff --git a/chameleonic.p8 b/chameleonic.p8
index 812c428..8688ebf 100644
--- a/chameleonic.p8
+++ b/chameleonic.p8
@@ -438,7 +438,9 @@ function level:spawn_exit()
   if (self:_mget(x,y)!=18) return
   for nx=x-1,x+1 do
    for ny=y-1,y+1 do
-    if nx<0 or ny<0 or nx>15 or ny>15 then
+    -- next check: is at least one of
+    -- nx or ny out of range [0, 15]?
+    if (nx | ny) & 0xFFF0 ~= 0 then
      self._wins[_mix(nx,ny)]=true
     end
    end
@@ -478,16 +480,18 @@ function _mix(mx,my)
   return mx..","..my
 end
 
+-- crate spec:
+-- "up" == 1
+-- "right" == 2
+-- "down" == 4
+-- "left" == 8
+--
+--    +1+
+--    8 2
+--    +4+
 function level:_get_cratedef(s)
- if (s<64 or s>=80) return nil
- 
- local s2=s-64
- return {
-  up=s2&1!=0,
-  right=s2&2!=0,
-  down=s2&4!=0,
-  left=s2&8!=0
- }
+ if (s<64 or s>=80) return
+ return s & 0x000F
 end
 
 function level:get_latch(dx,dy,px,py)
@@ -498,12 +502,7 @@ function level:get_latch(dx,dy,px,py)
  local dx1,dy1=-sgn0(dx),-sgn0(dy)
 
  if crate then
-  if
-   (crate.def.up and dy>0) or
-   (crate.def.down and dy<0) or 
-   (crate.def.left and dx>0) or
-   (crate.def.right and dx<0)
-  then
+  if crate.def & dy1*dy1*(2.5+1.5*dy1)+dx1*dx1*(5-3*dx1) ~= 0 then
    return {
     el="crate",
     dx=dx1,dy=dy1,
@@ -545,12 +544,12 @@ function level:can_move(
  if player.rope then
   local chk=false
   local w,h=1.6,0.2
-  if (dmx==0) w,h=0.2,1.6
-
-  if (dmy==-1) rectx,recty=0.4,-0.8
-  if (dmy==1) rectx,recty=0.4,0.2
-  if (dmx==-1) rectx,recty=-0.8,0.4
-  if (dmx==1) rectx,recty=0.2,0.4
+  if dmx==0 then 
+    w,h=0.2,1.6
+  else
+    dmy = 0
+  end
+  rectx,recty=dmx*(0.4>>>dmx),dmy*(0.4>>>dmy)
 
   if (player.rope:collide_mrect(mx0+rectx,my0+recty,w,h,exclude_src,exclude_dst)) return false
  end
@@ -627,7 +626,7 @@ function player:update()
   end
 
   if kbd:btn(4) then
-   if kbd:btnp(4) and self.rope!=nil then 
+   if kbd:btnp(4) and self.rope then 
     self.rope:destroy()
     kbd:release(4)
    end
@@ -660,7 +659,7 @@ function player:update()
     
     self.todo={{
      update=function()
-      return self.rope==nil or self.rope:latched()
+      return not self.rope or self.rope:latched()
      end
     }}
    elseif kbd:btnp(5) then
@@ -765,7 +764,7 @@ function player:draw()
 
  if self.rope then
   local rx_adj,ry_adj=self.rope:affected_src_xy(rx,ry)
-  if rx_adj!=nil then
+  if rx_adj then
    local drx,dry=rx_adj-rx,ry_adj-ry
    rx,ry=rx+drx,ry+dry
    px,py=px+drx,py+dry
@@ -833,10 +832,7 @@ function rope:update()
  elseif self.state.name=="latched" then
   if (self.latch==nil) wrongbleep:bleep(5) self:destroy() return
 
-  if 
-   self.latch!=nil and
-   self.latch.rec!=nil 
-  then
+  if self.latch and self.latch.rec then
    self:drag_src(
     self.latch.rec.mx+0.5+self.latch.ax_offset,
     self.latch.rec.my+0.5+self.latch.ay_offset
@@ -898,11 +894,10 @@ end
 
 function rope:draw(artificial_px,artificial_py)
  local points,highlight=self:_tug(true)
- if (self.state.name=="done") return
- local perc_to_show=1.0
- local from_end=false
- if (self.state.name=="cast") perc_to_show=self.state.frame/2
- if (self.state.name=="destroy") perc_to_show=(1.0-self.state.frame/8)^2
+ local n,perc_to_show,from_end = self.state.name,1.0,false
+ if (n=="done") return
+ if (n=="cast") perc_to_show=self.state.frame/2
+ if (n=="destroy") perc_to_show=(1.0-self.state.frame/8)^2
  if (self.state.reelin) from_end=true
 
  points[#points]={x=artificial_px,y=artificial_py}
@@ -1191,7 +1186,7 @@ function rope:be_pushed_by(anchor,ax_old,ay_old)
  local ax_new,ay_new=anchor.ax,anchor.ay
  while true do
   n1=n0.next
-  if (n1==nil) return
+  if (not n1) return
 
   local nx0,ny0=n0.ax,n0.ay
   local nx1,ny1=n1.ax,n1.ay
@@ -1318,7 +1313,7 @@ function _stepfrom(x0,x1)
  local done=false
  if x0==x1 then
   return function() 
-   if (done) return nil
+   if (done) return
    done=true return x0
   end
  end