diff --git a/public/js/main.js b/public/js/main.js
index b62d5b0..9087951 100644
--- a/public/js/main.js
+++ b/public/js/main.js
@@ -238,7 +238,6 @@
                     drawRobot(robot, ROBOT_COLORS[idx]);
                 }
             });
-
             if (currentWorld["next-shell-id"] !== previousWorld["next-shell-id"]) {
                 soundPlayers.shellRelease.play();
             }
diff --git a/src/robotwar/browser.clj b/src/robotwar/browser.clj
index a5180b6..2f28666 100644
--- a/src/robotwar/browser.clj
+++ b/src/robotwar/browser.clj
@@ -16,10 +16,8 @@
                                 :damage
                                 :shot-timer]))
           (select-shell-keys [shell]
-            (select-keys shell [:id
-                                :pos-x
-                                :pos-y
-                                :exploded]))
+            (select-keys shell [:pos-x
+                                :pos-y]))
           (three-sigs-map [m]
             (zipmap (keys m)
                     (map #(if (float? %)
diff --git a/src/robotwar/register.clj b/src/robotwar/register.clj
index 14a3eaf..ce526b8 100644
--- a/src/robotwar/register.clj
+++ b/src/robotwar/register.clj
@@ -123,7 +123,9 @@
                                              GAME-SECONDS-PER-SHOT)]
              (assoc 
                world-with-new-shot-timer
-               :shells (merge shells (shell/init-shell pos-x pos-y aim next-shell-id data))
+               :shells (merge 
+                         shells 
+                         {next-shell-id (shell/init-shell pos-x pos-y aim data)})
                :next-shell-id (inc next-shell-id))))))})
 
 (defn get-target-register
diff --git a/src/robotwar/shell.clj b/src/robotwar/shell.clj
index cb5e0d4..30272f4 100644
--- a/src/robotwar/shell.clj
+++ b/src/robotwar/shell.clj
@@ -3,32 +3,23 @@
   (:require [robotwar.physics :as physics]))
 
 (defn init-shell
-  [pos-x pos-y aim id distance]
-  ; TODO: make the starting point dependent upon the robot radius,
-  ; which should be in constants.
+  [pos-x pos-y aim distance]
   (let [{unit-x :x unit-y :y} (physics/decompose-angle aim)] 
-    {:id id
-     :pos-x pos-x
+    {:pos-x pos-x
      :pos-y pos-y
      :v-x (* unit-x SHELL-SPEED)
      :v-y (* unit-y SHELL-SPEED)
      :dest-x (+ pos-x (* unit-x distance))
-     :dest-y (+ pos-y (* unit-y distance))
-     :exploded false})) 
+     :dest-y (+ pos-y (* unit-y distance))}))
 
 (defn tick-shell
-  [{:keys [pos-x pos-y v-x v-y dest-x dest-y exploded] :as shell}]
-  (if exploded
-    nil
-    (let [delta-x (* v-x *GAME-SECONDS-PER-TICK*)
-          delta-y (* v-y *GAME-SECONDS-PER-TICK*)
-          remaining-x (- dest-x pos-x)
-          remaining-y (- dest-y pos-y)]
-      ; only need to check one dimension
-      (if (and (<= (Math/abs remaining-x) (Math/abs delta-x))
-               (<= (Math/abs remaining-y) (Math/abs delta-y)))
-        (merge shell {:pos-x dest-x
-                      :pos-y dest-y
-                      :exploded true})
-        (merge shell {:pos-x (+ pos-x delta-x)
-                      :pos-y (+ pos-y delta-y)})))))
+  [{:keys [pos-x pos-y v-x v-y dest-x dest-y] :as shell}]
+  (let [delta-x (* v-x *GAME-SECONDS-PER-TICK*)
+        delta-y (* v-y *GAME-SECONDS-PER-TICK*)
+        remaining-x (- dest-x pos-x)
+        remaining-y (- dest-y pos-y)]
+    (if (and (<= (Math/abs remaining-x) (Math/abs delta-x))
+             (<= (Math/abs remaining-y) (Math/abs delta-y)))
+      nil
+      (merge shell {:pos-x (+ pos-x delta-x)
+                    :pos-y (+ pos-y delta-y)}))))
diff --git a/src/robotwar/world.clj b/src/robotwar/world.clj
index f57ed92..fbc2575 100644
--- a/src/robotwar/world.clj
+++ b/src/robotwar/world.clj
@@ -25,16 +25,18 @@
 (defn tick-combined-world
   [starting-world]
   (let [{:keys [shells next-shell-id] :as ticked-robots-world} 
-          (reduce (fn [{robots :robots :as world} robot-idx]
-                    (robot/tick-robot (robots robot-idx) world))
-                  starting-world
-                  (range (count (:robots starting-world))))
-        ticked-shells (map shell/tick-shell shells)
-        live-shells (remove :exploded ticked-shells)
-        exploded-shells (filter :exploded ticked-shells)]
+        (reduce (fn [{robots :robots :as world} robot-idx]
+                  (robot/tick-robot (robots robot-idx) world))
+                starting-world
+                (range (count (:robots starting-world))))
+        ticked-shells (into {} (map (fn [shell-map-entry]
+                                      [(key shell-map-entry)
+                                       (shell/tick-shell (val shell-map-entry))])
+                                    shells))]
     ; TODO: make this a real let-binding, that determines
     ; which robots were damaged.
     (let [damaged-world ticked-robots-world]
-      (assoc damaged-world :shells live-shells))))
+      (pprint ticked-shells)
+      (assoc damaged-world :shells ticked-shells))))
 
 (def build-combined-worlds (partial iterate tick-combined-world))