diff --git a/src/robotwar/register.clj b/src/robotwar/register.clj
index ae82f7f..30b2883 100644
--- a/src/robotwar/register.clj
+++ b/src/robotwar/register.clj
@@ -20,73 +20,80 @@
 (defn path-to-val [robot-idx reg-name]
   [:robots robot-idx :registers reg-name :val])
 
-(defprotocol IRegister
-  (read-register [this world])
+(defprotocol IReadRegister
+  "returns the value of a register"
+  (read-register [this world]))
+
+(defprotocol IWriteRegister
+  "returns a world"
   (write-register [this world data]))
 
-(defrecord StorageRegister [robot-idx reg-name val]
-  IRegister
-  (read-register 
-    "returns value stored in register"
-    [this world]
-    val)
-  (write-register 
-    "returns world with value in register altered"
-    [this world data]
-    (assoc-in world (path-to-val robot-idx reg-name) data))) 
+(def default-read-mixin
+  ; returns :val field of register
+  {:read-register (fn [this world]
+                    (:val this))})
 
-(defrecord ReadOnlyRegister [robot-idx field-name]
-  IRegister
-  (read-register 
-    "returns the value in a particular robot field" 
-    [this world]
-    (get-in world (conj (path-to-robot robot-idx) field-name)))
-  (write-register 
-    "has no effect (returns the world it was given)" 
-    [this world data]
-    world))
+(def default-write-mixin
+  ; returns a world with :val field of register altered
+  {:write-register (fn [this world data]
+                     (assoc-in world 
+                               (path-to-val (:robot-idx this) (:reg-name this))
+                               data))})
 
-(defn target-register
+(def robot-field-read-mixin
+  ; returns the value of a field in the robot hash-map
+  {:read-register (fn [this world]
+                    (get-in world (conj path-to-robot (:field-name this))))})
+
+(def no-op-write-mixin
+  ; returns a world with nothing changed
+  {:write-register (fn [this world data] 
+                     world)})
+
+(def random-read-mixin
+  ; returns a random number. maximum value is the :val field of the register
+  {:read-register (fn [this world]
+                    (rand-int (:val this)))})
+
+(defrecord StorageRegister [robot-idx reg-name val])
+(extend StorageRegister
+  IReadRegister default-read-mixin
+  IWriteRegister default-write-mixin)
+
+(defrecord ReadOnlyRegister [robot-idx field-name])
+(extend ReadOnlyRegister
+  IReadRegister robot-field-read-mixin
+  IWriteRegister no-op-write-mixin)
+
+(defrecord RandomRegister [robot-idx reg-name val])
+(extend RandomRegister
+  IReadRegister random-read-mixin
+  IWriteRegister default-write-mixin)
+
+(defn get-target-register
   "helper function for DataRegister record"
   [world robot-idx index-reg-name]
   (let [registers (get-in world (path-to-registers robot-idx))]
     (registers (reg-names (read-register (registers index-reg-name) world)))))
 
 (defrecord DataRegister [robot-idx index-reg-name]
-  IRegister
+  IReadRegister
   (read-register
-    "returns the number stored in whatever register 
-    is pointed to by the index-reg-name register"
+    ; returns the number stored in whatever register 
+    ; is pointed to by the index-reg-name register
     [this world]
-    (read-register (target-register world robot-idx index-reg-name) world))
+    (read-register (get-target-register world robot-idx index-reg-name) world))
+  IWriteRegister
   (write-register
-    "returns a world with the number in the register pointed to 
-    by the index-reg-name register updated with the data argument to write-register"
+    ; returns a world with the number in the register pointed to 
+    ; by the index-reg-name register updated with the data argument to write-register
     [this world data]
-    (write-register (target-register world robot-idx index-reg-name) world data)))
-
-; TODO: (defrecord RandomRegister [robot-idx reg-name max-rand])
+    (write-register (get-target-register world robot-idx index-reg-name) world data)))
 
 ; TODO: (defrecord ShotRegister [robot-idx reg-name])
 
 ; TODO: (defrecord RadarRegister [robot-idx reg-name])
 
-;           ; RANDOM
-;           (init-register "RANDOM" robot-idx
-;                          (fn [world path-to-val]
-;                            (rand-int (get-in world path-to-val)))
-;                          assoc-in
-;                          0)
-;
-;           ; X and Y and DAMAGE
-;           (init-read-only-register "X" robot-idx :pos-x (:pos-x attributes))
-;           (init-read-only-register "Y" robot-idx :pos-y (:pos-y attributes))
-;           (init-read-only-register "DAMAGE" robot-idx :damage (:damage attributes))])))
-;
-;           ; TODO: SHOT AND RADAR
-
-
-
 (defn init-registers
   "AIM, INDEX, SPEEDX and SPEEDY.
   AIM and INDEX's specialized behaviors are only when they're used by
@@ -104,7 +111,7 @@
                       {"Y"      (->ReadOnlyRegister robot-idx :pos-y)}
                       {"DAMAGE" (->ReadOnlyRegister robot-idx :damage)}
                       {"DATA"   (->DataRegister robot-idx "INDEX")}
-                      ; TODO: {"RANDOM" (->RandomRegister robot-idx "RANDOM" 0)}
+                      {"RANDOM" (->RandomRegister robot-idx "RANDOM" 0)}
                       ; TODO: {"SHOT"   (->ShotRegister robot-idx "SHOT")}
                       ; TODO: {"RADAR"  (->RadarRegister robot-idx "RADAR")}
                       ]))))