diff --git a/chameleonic.p8 b/chameleonic.p8
index 23abe38..0c90110 100644
--- a/chameleonic.p8
+++ b/chameleonic.p8
@@ -129,11 +129,12 @@ end
 
 
 function _rast(
- xs,ys,x0,y0,x1,y1
+ xys,x0,y0,x1,y1
 )
  local function _add()
-  local n=#xs
-  if (n==0 or xs[n]!=x0 or ys[n]!=y0) add(xs,x0) add(ys,y0)
+  local n=#xys
+  local xy0={x0,y0}
+  if (n==0 or not _anch_eq(xys[n],xy0)) add(xys,xy0)
  end
 
  local dx,dy=abs(x1-x0),abs(y1-y0)
@@ -432,10 +433,10 @@ function level:recollide_reanchor()
     local mx1,my1=mx0+dx,my0+dy
 
     if (
-     self:mcoll(mx0,my0) and not self:get_crate(mx0,my0) and
-     not self:mcoll(mx0,my1) and
-     not self:mcoll(mx1,my0) and
-     not self:mcoll(mx1,my1)
+     self:mcoll{mx0,my0} and not self:get_crate(mx0,my0) and
+     not self:mcoll{mx0,my1} and
+     not self:mcoll{mx1,my0} and
+     not self:mcoll{mx1,my1}
     ) then
      local key=_mix{"GEOM",mx0,my0,dx,dy}
      anch_new[key]= {
@@ -543,7 +544,8 @@ function level:spawn_exit()
  assert(spawned)
 end
 
-function level:mcoll(mx,my)
+function level:mcoll(mxy)
+ local mx,my=unpack(mxy)
  if ((mx | my) & 0xFFF0!=0) return true
  return self._coll[_mix{mx,my}]
 end
@@ -628,7 +630,7 @@ function level:can_move(
  if (is_player and self:win_at(mx1,my1)) return true 
  if (is_player and self:get_open_pit(mx1,my1)) return wrongbleep:adequately_warned()
 
- if (self:mcoll(mx1,my1) or player.x==mx1 and player.y==my1) return 
+ if (self:mcoll{mx1,my1} or player.x==mx1 and player.y==my1) return 
 
  if player.rope then
   local w,h=1.2,0.2
@@ -748,7 +750,7 @@ function player:update()
     local dx,dy=self.orientx,self.orienty
     if (dy!=0) dx=0
 
-    while not level:mcoll(x,y) do x+=dx y+=dy end
+    while not level:mcoll{x,y} do x+=dx y+=dy end
 
     self.rope=rope:new(
      {x+0.5-dx*0.5,y+0.5-dy*0.5},
@@ -1131,60 +1133,43 @@ function rope:_check_pinch()
 
  local n0=self.src
 
- local qxs,qys={},{}
+ local qxys={}
  while true do 
   local n1=n0.next
   if (not n1) break 
 
   local n0ax,n0ay=_anch_unpack(n0)
   local n1ax,n1ay=_anch_unpack(n1)
-  _rast(qxs,qys,flr(n0ax*2),flr(n0ay*2),flr(n1ax*2),flr(n1ay*2)) 
+  _rast(qxys,n0ax\0.5,n0ay\0.5,n1ax\0.5,n1ay\0.5) 
   n0=n1
  end
 
- local function _possible_tiles(qx,qy)
-  local mx0=(qx-1)\2
-  local mx1=qx\2
-  local my0=(qy-1)\2
-  local my1=qy\2
-
+ local function _possible_tiles(t)
+  local qx,qy=unpack(qxys[t])
   local poss={}
-  for mx=mx0,mx1 do
-   for my=my0,my1 do
-    add(poss,{mx=mx,my=my})
+  for mx=(qx-1)\2,qx\2 do
+   for my=(qy-1)\2,qy\2 do
+    if (not level:mcoll{mx,my}) add(poss,{mx,my})
    end
   end
-  return poss
- end
- local function _blocked(qx,qy)
-  for i in all(_possible_tiles(qx,qy)) do
-   if (not level:mcoll(i.mx,i.my)) return 
-  end
-  return true
+  return all(poss)
  end
 
  -- find cases where i move through an impassable zone
- for i=1,#qxs do
-  if (_blocked(qxs[i],qys[i])) return 
+ for i=1,#qxys do
+  if (not _possible_tiles(i)()) return 
  end
 
  -- find cases where i am cut off diagonally
- for i=3,#qxs do
-  local qx1,qy1=qxs[i-1],qys[i-1]
-  if qx1%2==0 and qy1%2==0 then
+ for i=3,#qxys do
+  local qx1,qy1=unpack(qxys[i-1])
+  if (qx1|qy1)&1==0 then
    local ok
-   for m0 in all(_possible_tiles(qxs[i-2],qys[i-2])) do
-    for m2 in all(_possible_tiles(qxs[i],qys[i])) do
-     local mx0,my0=m0.mx,m0.my
-     local mx2,my2=m2.mx,m2.my
-     if not (level:mcoll(mx0,my0) or level:mcoll(mx2,my2)) then
-      local dmx,dmy=abs(mx2-mx0),abs(my2-my0)
-
-      if dmx==1 and dmy==1 and level:mcoll(mx0,my2) and level:mcoll(mx2,my0) then
-      else
-       ok=true
-      end
-     end
+   for m0 in _possible_tiles(i-2) do
+    for m2 in _possible_tiles(i) do
+     local mx0,my0=unpack(m0)
+     local mx2,my2=unpack(m2)
+     if (mx0==mx2 or my0==my2 or not level:mcoll{mx0,my2} or not level:mcoll{mx2,my0}) ok=true
     end
    end
 
@@ -1631,7 +1616,7 @@ function rope:_calc_push(
  local ops2,blocked={},{}
  for o in all(ops) do
   local mx,my=unpack(o)
-  if level:mcoll(mx,my) then
+  if level:mcoll{mx,my} then
    if (not level:get_crate(mx, my)) break
    if not level:can_move(false,o,0,0) then
     add(blocked,o)