diff --git a/src/bullet.lua b/src/bullet.lua
index 7b8682a..b8cfc51 100644
--- a/src/bullet.lua
+++ b/src/bullet.lua
@@ -7,20 +7,24 @@ local gfx <const> = playdate.graphics
 
 class("Bullet").extends(gfx.sprite)
 
+local POWER_SIZE_LOOKUP <const> = {
+   [1] = 2,
+   [2] = 4,
+   [3] = 6,
+   [4] = 10,
+}
+
+local POWER_DAMAGE_LOOKUP <const> = {
+   [1] = 1,
+   [2] = 3,
+   [3] = 5,
+   [4] = 10,
+}
+
 function Bullet:init(power, friendly)
    Bullet.super.init(self)
    self.power = power
-
-   local size = 1
-   if power == 1 then
-      size = 2
-   elseif power == 2 then
-      size = 4
-   elseif power == 3 then
-      size = 6
-   elseif power == 4 then
-      size = 10
-   end
+   local size = POWER_SIZE_LOOKUP[power]
 
    local img = gfx.image.new(size, size)
    gfx.pushContext(img)
@@ -44,5 +48,14 @@ function Bullet:init(power, friendly)
 end
 
 function Bullet:update()
-   self:moveWithCollisions(self.x+self.direction, self.y)
+   local collisions = select(3, self:moveWithCollisions(self.x+self.direction, self.y))
+   for i=1, #collisions, 1 do
+      -- anything the bullet can collide with should be damaged by it
+      local obj = collisions[i].other
+      obj:damage(POWER_DAMAGE_LOOKUP[self.power])
+   end
+
+   if #collisions >= 1 then
+      self:remove()
+   end
 end
diff --git a/src/entity.lua b/src/entity.lua
new file mode 100644
index 0000000..66c926f
--- /dev/null
+++ b/src/entity.lua
@@ -0,0 +1,28 @@
+-- A superclass for all player and AI-controlled units
+import "CoreLibs/object"
+import "CoreLibs/graphics"
+import "CoreLibs/sprites"
+
+local gfx <const> = playdate.graphics
+
+class("Entity").extends(gfx.sprite)
+
+function Entity:init(img, health)
+   Entity.super.init(self, img)
+   self.health = health or 10
+
+   self:setCollideRect(0, 0, self:getSize())
+
+   -- most entities will be enemies, so we configure this mask by default
+   -- We don't set a collider mask because collision is always handled by
+   -- other objects (todo: consider player staying perfectly still)
+   self:setGroupMask(0x8)
+end
+
+function Entity:damage(amount)
+   self.health = math.max(self.health - amount, 0)
+
+   if self.health == 0 then
+      self:remove()
+   end
+end
diff --git a/src/ika.lua b/src/ika.lua
new file mode 100644
index 0000000..5bc8905
--- /dev/null
+++ b/src/ika.lua
@@ -0,0 +1,14 @@
+-- A squid-like enemy unit
+import "CoreLibs/object"
+import "CoreLibs/graphics"
+import "CoreLibs/sprites"
+import "entity"
+
+local gfx <const> = playdate.graphics
+
+class("Ika").extends(Entity)
+
+function Ika:init()
+   local img = gfx.image.new(30, 30, gfx.kColorBlack)
+   Ika.super.init(self, img, 25)
+end
diff --git a/src/kani.lua b/src/kani.lua
index 21c18e2..e00fa06 100644
--- a/src/kani.lua
+++ b/src/kani.lua
@@ -3,6 +3,7 @@ import "CoreLibs/object"
 import "CoreLibs/graphics"
 import "CoreLibs/sprites"
 import "CoreLibs/timer"
+import "entity"
 import "bullet"
 import "ui"
 
@@ -19,19 +20,16 @@ local WEAPON_CHARGE_LOOKUP <const> = {
    [3]=50
 }
 
-class("Kani").extends(gfx.sprite)
+class("Kani").extends(Entity)
 
 function Kani:init(ui)
    local img = gfx.image.new("images/kani.png")
-   Kani.super.init(self, img)
+   Kani.super.init(self, img, 100)
 
-   self:setCollideRect(0, 0, self:getSize())
    self.vector = {x=0,y=0} -- movement direction
    self:setGroupMask(0x2)
    self:setCollidesWithGroupsMask(0x19)
 
-   -- stats
-   self.health = 100
    self.reserveCharge = 100
 
    -- controls the speed the crank recharges the player's reserves. A lower number allows faster charging.
@@ -106,12 +104,12 @@ function Kani:fire()
 end
 
 function Kani:damage(amount)
-   self.health = math.max(self.health - amount, 0)
-
-   if self.health <= 0 then
-      -- TODO: destroy ship
-   end
+   Kani.super.damage(self, amount)
    self.ui.healthMeter:setValue(self.health)
+
+   if self.health == 0 then
+      -- TODO: end game here
+   end
 end
 
 function Kani:addInputHandlers()
diff --git a/src/main.lua b/src/main.lua
index 5d70bb1..ad9e897 100644
--- a/src/main.lua
+++ b/src/main.lua
@@ -9,6 +9,7 @@ import "CoreLibs/graphics"
 import "CoreLibs/sprites"
 import "CoreLibs/timer"
 import "kani"
+import "ika"
 
 local gfx <const> = playdate.graphics
 
@@ -23,6 +24,10 @@ function setup()
    player:add()
    ui:add()
 
+   local enemy = Ika()
+   enemy:moveTo(350, 120)
+   enemy:add()
+
    makeWalls()
    
    drawBackground()
diff --git a/src/pipmeter.lua b/src/pipmeter.lua
index d4c2eff..61d9412 100644
--- a/src/pipmeter.lua
+++ b/src/pipmeter.lua
@@ -21,7 +21,7 @@ function PipMeter:init(initialValue, numPips, baseSize, sizeIncrement, spacing,
    local width = (numPips * (padBaseSize + lastSize)) / 2 - spacing
    self:setSize(width, lastSize)
 
-   if self.circle then
+   if circle then
       self.drawFunc = gfx.drawCircleInRect
       self.fillFunc = gfx.fillCircleInRect
    else
@@ -39,8 +39,6 @@ function PipMeter:setValue(value)
       for i=1, self.numPips, 1 do
          local size = self.baseSize+(self.sizeIncrement*(i-1))
 
-         print(string.format("Drawing a pip with %d %d %d %d", offset, self.height, size, size))
-            
          if value >= i then
             self.fillFunc(offset, self.height - size, size, size)
          else
diff --git a/src/ui.lua b/src/ui.lua
index 338b2bb..8782947 100644
--- a/src/ui.lua
+++ b/src/ui.lua
@@ -9,7 +9,7 @@ class("UI", {}).extends(playdate.object)
 function UI:init()
    self.chargeMeter = Meter(100, 10, 60)
    self.healthMeter = Meter(100, 60, 10, false)
-   self.weaponPowerMeter = PipMeter(0, 4, 5, 3, 3)
+   self.weaponPowerMeter = PipMeter(0, 4, 4, 4, 3, true)
    self:moveTo(359, 199)
 end