Add some object-oriented sensibilities into this mess.

pixie.lua

@@ -0,0 +1,71 @@
+-- A pixie is like a sprite, but better
+
+import "CoreLibs/object"
+import "CoreLibs/graphics"
+import "CoreLibs/sprites"
+
+local gfx <const> = playdate.graphics
+
+class("Pixie").extends(gfx.sprite)
+
+-- Crong pixies are simple rectangles, so they take an initial position, width, height, and color
+-- They are also collidable
+function Pixie:init(width, height, color, x, y)
+   x = x or 0
+   y = y or 0
+
+   Pixie.super.init(self, gfx.image.new(width, height, color))
+   self:setCollideRect(0, 0, self:getSize())
+   self:moveTo(x, y)
+   return self
+end
+
+function Pixie:moveTo(x, y)
+   Pixie.super.moveTo(self, x, y)
+   self:_normalizePosition()
+end
+
+function Pixie:moveBy(x, y)
+   Pixie.super.moveBy(self, x, y)
+   self:_normalizePosition()
+end
+
+function Pixie:_normalizePosition()
+   local limitTop = self.height / 2
+   local limitBottom = 240 - limitTop
+   local limitLeft = self.width / 2
+   local limitRight = 400 - limitLeft
+
+   local changedX = 0
+   local changedY = 0
+   local newX = self.x
+   local newY = self.y
+   
+   if self.y < limitTop then
+      newY = limitTop
+      changedY = 1
+   end
+
+   if self.y > limitBottom then
+      newY = limitBottom
+      changedY = -1
+   end
+
+   if self.x < limitLeft then
+      newX = limitLeft
+      changedX = 1
+   end
+
+   if self.x > limitRight then
+      newX = limitRight
+      changedX = -1
+   end
+
+   if changedX ~= 0 or changedY ~= 0 then
+      -- call super to avoid the odd possibility that we recurse back into
+      -- this function
+      Pixie.super.moveTo(self, newX, newY)
+   end
+
+   return {changedX, changedY}
+end