diff --git a/extra/boids/boids.factor b/extra/boids/boids.factor
index e6c97b90dd..cff33c9d19 100644
--- a/extra/boids/boids.factor
+++ b/extra/boids/boids.factor
@@ -6,14 +6,17 @@ USING: combinators.short-circuit kernel namespaces
        math.order
        math.vectors
        math.trig
+       math.physics.pos
+       math.physics.vel
        combinators arrays sequences random vars
-       combinators.lib ;
+       combinators.lib
+       accessors ;
 
 IN: boids
 
 ! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
 
-TUPLE: boid pos vel ;
+TUPLE: boid < vel ;
 
 C: <boid> boid
 
@@ -70,7 +73,7 @@ VAR: separation-radius
 
 ! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
 
-: distance ( boid boid -- n ) [ boid-pos ] [ boid-pos ] bi* v- norm ;
+: distance ( boid boid -- n ) [ pos>> ] [ pos>> ] bi* v- norm ;
 
 ! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
 
@@ -81,10 +84,10 @@ VAR: separation-radius
 
 ! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
 
-: relative-position ( self other -- v ) swap [ boid-pos ] bi@ v- ;
+: relative-position ( self other -- v ) swap [ pos>> ] bi@ v- ;
 
 : relative-angle ( self other -- angle )
-over boid-vel -rot relative-position angle-between ;
+over vel>> -rot relative-position angle-between ;
 
 ! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
 
@@ -92,9 +95,9 @@ over boid-vel -rot relative-position angle-between ;
 
 : vaverage ( seq-of-vectors -- seq ) [ vsum ] [ length ] bi v/n ;
 
-: average-position ( boids -- pos ) [ boid-pos ] map vaverage ;
+: average-position ( boids -- pos ) [ pos>> ] map vaverage ;
 
-: average-velocity ( boids -- vel ) [ boid-vel ] map vaverage ;
+: average-velocity ( boids -- vel ) [ vel>> ] map vaverage ;
 
 ! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
 
@@ -123,7 +126,7 @@ over boid-vel -rot relative-position angle-between ;
   dup cohesion-neighborhood
   dup empty?
   [ 2drop { 0 0 } ]
-  [ average-position swap boid-pos v- normalize* cohesion-weight> v*n ]
+  [ average-position swap pos>> v- normalize* cohesion-weight> v*n ]
   if ;
 
 ! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
@@ -143,7 +146,7 @@ over boid-vel -rot relative-position angle-between ;
   dup separation-neighborhood
   dup empty?
   [ 2drop { 0 0 } ]
-  [ average-position swap boid-pos swap v- normalize* separation-weight> v*n ]
+  [ average-position swap pos>> swap v- normalize* separation-weight> v*n ]
   if ;
 
 ! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
@@ -206,10 +209,10 @@ cond ;
 
 ! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
 
-: new-pos ( boid -- pos ) [ boid-pos ] [ boid-vel time-slice> v*n ] bi v+ ;
+: new-pos ( boid -- pos ) [ pos>> ] [ vel>> time-slice> v*n ] bi v+ ;
 
 : new-vel ( boid -- vel )
-  [ boid-vel ] [ acceleration time-slice> v*n ] bi v+ normalize* ;
+  [ vel>> ] [ acceleration time-slice> v*n ] bi v+ normalize* ;
 
 : wrap-pos ( pos -- pos ) { [ wrap-x ] [ wrap-y ] } parallel-call ;
 
diff --git a/extra/boids/ui/ui.factor b/extra/boids/ui/ui.factor
index e3c54e0744..ab1f8e5f80 100755
--- a/extra/boids/ui/ui.factor
+++ b/extra/boids/ui/ui.factor
@@ -19,7 +19,8 @@ USING: combinators.short-circuit kernel namespaces
        ui.gadgets.packs
        ui.gadgets.grids
        ui.gestures
-       assocs.lib vars rewrite-closures boids ;
+       assocs.lib vars rewrite-closures boids accessors
+       math.geometry.rect ;
 
 IN: boids.ui
 
@@ -27,9 +28,9 @@ IN: boids.ui
 ! draw-boid
 ! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
 
-: point-a ( boid -- a ) boid-pos ;
+: point-a ( boid -- a ) pos>> ;
 
-: point-b ( boid -- b ) [ boid-pos ] [ boid-vel normalize* 20 v*n ] bi v+ ;
+: point-b ( boid -- b ) [ pos>> ] [ vel>> normalize* 20 v*n ] bi v+ ;
 
 : boid-points ( boid -- point-a point-b ) [ point-a ] [ point-b ] bi ;