main.lua, etc. - use a sorted list of mobs

The mobs are characters to animate.  They're sorted by screen depth,
so that nearer ones render over farther ones.

arena.lua

@@ -52,6 +52,8 @@ return function(size, discs, topCol, rightCol, leftCol)
    end
 
    return {
+      getDepth = function() return -1; end,
+      
       getWidth = function()
 	 return size*width*2
       end,

hopper.lua

@@ -162,6 +162,8 @@ return function(arena, draw, update)
    local se, sw = 0, 0
    local jumpPath = newJumpPath(arena.getColWidth(), arena.getRowHeight())
    return {
+      getDepth = function() return sw+se; end,
+      
       jump = function(dir)
 	 if jumpTime ~= nil then
 	    return -- already jumping

main.lua

@@ -11,27 +11,22 @@ local time = 0
 local qbert = mkQbert(
    arena
 )
+local mobs = { qbert, arena }
 
 function love.load()
 
 end
 
 function love.draw()
-   arena.draw()
-   qbert.draw()
+   for ix, mob in ipairs(mobs) do
+      mob.draw()
+   end
 end
 
-local dirs = {"se", "sw", "ne", "nw"}
-local ix = 1
+
+
 function love.update(dt)
---[[   time = time + dt
-   if (time > 2) then
-      time = 0
-      local dir = dirs[ix]
-      ix = (ix+1)%4 + 1
-      qbert.jump(dir)
-   end
-]]--
+
    if love.keyboard.isDown('i') then
       qbert.jump('ne')
    end
@@ -44,7 +39,22 @@ function love.update(dt)
    if love.keyboard.isDown('j') then
       qbert.jump('sw')
    end
+   if love.keyboard.isDown('escape') then
+      love.event.quit(0)
+   end
    
-   arena.update(dt);
-   qbert.update(dt);
+
+   for ix, mob in ipairs(mobs) do
+      mob.update(dt)
+   end
+
+   local mobs2 = {}
+   for ix, mob in ipairs(mobs) do
+      if not mob.dead then
+	 mobs2[#mobs2+1] = mob
+      end
+   end
+
+   table.sort(mobs2, function(a, b) return a.getDepth() < b.getDepth(); end)
+   mobs = mobs2
 end