From 3930b2b5d45f96dc3e52f2b60fcc34279bb7820e Mon Sep 17 00:00:00 2001
From: parameterized <troyk212@gmail.com>
Date: Fri, 21 Sep 2018 03:35:00 -0400
Subject: [PATCH] sort draw order by y/layer/type

---
 entities.lua         |  22 ++++--
 entityDefs/slime.lua |   8 +-
 hud.lua              |   9 +++
 loadassets.lua       |   1 +
 lootBags.lua         |  70 ++++++++---------
 main.lua             |  17 ++++-
 menu.lua             |   3 +-
 player.lua           | 178 +++++++++++++++++++++++--------------------
 projectiles.lua      |  57 +++++++-------
 scene.lua            |  39 ++++++++++
 utils.lua            |  24 ++++++
 11 files changed, 273 insertions(+), 155 deletions(-)
 create mode 100644 scene.lua

diff --git a/entities.lua b/entities.lua
index 270f6e3..54b2ff2 100644
--- a/entities.lua
+++ b/entities.lua
@@ -61,12 +61,22 @@ end
 function entities.client.draw()
     for _, v in pairs(client.currentState.entities) do
         if not v.destroyed and v.drawBody then
-            v:drawBody()
-        end
-    end
-    for _, v in pairs(client.currentState.entities) do
-        if not v.destroyed and v.drawHP then
-            v:drawHP()
+            scene.add{
+                draw = function()
+                    v:drawBody()
+                end,
+                y = v.y,
+                type = 'entityBody'
+            }
+            if v.drawHP then
+                scene.add{
+                    draw = function()
+                        v:drawHP()
+                    end,
+                    y = v.y,
+                    type = 'entityHP'
+                }
+            end
         end
     end
 end
diff --git a/entityDefs/slime.lua b/entityDefs/slime.lua
index 2f64f25..adefc1e 100644
--- a/entityDefs/slime.lua
+++ b/entityDefs/slime.lua
@@ -41,7 +41,7 @@ function slime.server:spawn()
             if (i2-1) % 2 == 0 then -- x
                 v[i2] = v2*img:getWidth() - img:getWidth()/2
             else
-                v[i2] = v2*img:getWidth()*-1 + img:getHeight()/2
+                v[i2] = v2*img:getWidth()*-1
             end
         end
     end
@@ -156,7 +156,7 @@ function slime.client:spawn()
             if (i2-1) % 2 == 0 then -- x
                 v[i2] = v2*img:getWidth() - img:getWidth()/2
             else
-                v[i2] = v2*img:getWidth()*-1 + img:getHeight()/2
+                v[i2] = v2*img:getWidth()*-1
             end
         end
     end
@@ -215,7 +215,7 @@ function slime.client:drawBody()
     love.graphics.draw(img,
         0, 0,
         0, 1, 1,
-        lume.round(img:getWidth()/2), lume.round(img:getHeight()/2))
+        lume.round(img:getWidth()/2), img:getHeight())
     love.graphics.pop()
     love.graphics.setShader(_shader)
 end
@@ -236,7 +236,7 @@ function slime.client:drawHP()
     love.graphics.push()
     local vx, vy = self.body:getPosition()
     love.graphics.translate(lume.round(vx), lume.round(vy))
-    love.graphics.draw(canvases.hpBar, lume.round(-canvases.hpBar:getWidth()/2), 10)
+    love.graphics.draw(canvases.hpBar, lume.round(-canvases.hpBar:getWidth()/2), 2)
     love.graphics.pop()
 end
 
diff --git a/hud.lua b/hud.lua
index 1dfc44e..5823f12 100644
--- a/hud.lua
+++ b/hud.lua
@@ -149,6 +149,7 @@ end
 
 function hud.mousepressed(mx, my, btn)
     mx, my = window2game(mx, my)
+    mx, my = lume.round(mx), lume.round(my)
     local chatFieldPressed = false
     for _, v in pairs(hud.buttons) do
         if mx > v.x and mx < v.x + v.img:getWidth() and my > v.y and my < v.y + v.img:getHeight() then
@@ -168,6 +169,7 @@ end
 
 function hud.draw()
     local mx, my = window2game(love.mouse.getPosition())
+    mx, my = lume.round(mx), lume.round(my)
 
     love.graphics.setColor(1, 1, 1)
     love.graphics.draw(gfx.hud.frame, 0, 0)
@@ -230,4 +232,11 @@ function hud.draw()
     love.graphics.setColor(1, 1, 1)
     love.graphics.setFont(fonts.c17)
     text.print(player.name, 44, 5)
+
+    -- draggables
+    local heldItem = lootBags.client.heldItem
+    if heldItem.bagId then
+        love.graphics.setColor(1, 1, 1, 0.8)
+        love.graphics.rectangle('fill', mx + heldItem.offset.x, my + heldItem.offset.y, 15, 15)
+    end
 end
diff --git a/loadassets.lua b/loadassets.lua
index 298fd55..3f8adf1 100644
--- a/loadassets.lua
+++ b/loadassets.lua
@@ -6,6 +6,7 @@ math.randomseed(love.timer.getTime())
 
 love.keyboard.setKeyRepeat(true)
 love.graphics.setDefaultFilter('nearest', 'nearest')
+love.graphics.setLineStyle('rough')
 
 gsx, gsy = 480, 270
 canvases = {
diff --git a/lootBags.lua b/lootBags.lua
index 44e52b1..050d74a 100644
--- a/lootBags.lua
+++ b/lootBags.lua
@@ -135,41 +135,41 @@ function lootBags.client.draw()
     mx, my = lume.round(mx), lume.round(my)
     mx, my = camera:screen2world(mx, my)
     for _, bag in pairs(client.currentState.lootBags) do
-        local a = 1
-        if bag.life and client.serverTime - bag.spawnTime > bag.life - 3 then
-            local t = (client.serverTime - bag.spawnTime - bag.life + 3)/3
-            a = math.cos(t*5*math.pi)/4 + 1/4 + (1-t)/2
-        end
-        love.graphics.setColor(1, 1, 1, a)
-        love.graphics.push()
-        love.graphics.translate(lume.round(bag.x), lume.round(bag.y))
-        local img = gfx.items[bag.type]
-        love.graphics.draw(img, 0, 0, 0, 1, 1, lume.round(img:getWidth()/2), img:getHeight())
-        if bag.id == lootBags.client.closest.id and lootBags.client.closest.dist < 30 then
-            local img = gfx.ui.bag
-            love.graphics.push()
-            love.graphics.translate(-lume.round(img:getWidth()/2), -img:getHeight() - 20)
-            love.graphics.draw(img, 0, 0)
-            local bmx = mx - (lume.round(bag.x) - lume.round(img:getWidth()/2))
-            local bmy = my - (lume.round(bag.y) - img:getHeight() - 20)
-            for _, slot in ipairs(lootBags.client.slots) do
-                if bmx >= slot.x and bmx <= slot.x + slot.w
-                and bmy >= slot.y and bmy <= slot.y + slot.h then
-                    love.graphics.setColor(1, 1, 1, 0.8)
-                else
-                    love.graphics.setColor(1, 1, 1, 0.2)
+        scene.add{
+            draw = function()
+                local a = 1
+                if bag.life and client.serverTime - bag.spawnTime > bag.life - 3 then
+                    local t = (client.serverTime - bag.spawnTime - bag.life + 3)/3
+                    a = math.cos(t*5*math.pi)/4 + 1/4 + (1-t)/2
                 end
-                love.graphics.rectangle('fill', slot.x, slot.y, slot.w, slot.h)
-            end
-            love.graphics.setColor(1, 0, 0, 0.4)
-            love.graphics.rectangle('fill', bmx, bmy, 2, 2)
-            love.graphics.pop()
-        end
-        love.graphics.pop()
-    end
-    local heldItem = lootBags.client.heldItem
-    if heldItem.bagId then
-        love.graphics.setColor(1, 1, 1, 0.8)
-        love.graphics.rectangle('fill', mx + heldItem.offset.x, my + heldItem.offset.y, 15, 15)
+                love.graphics.setColor(1, 1, 1, a)
+                love.graphics.push()
+                love.graphics.translate(lume.round(bag.x), lume.round(bag.y))
+                local img = gfx.items[bag.type]
+                love.graphics.draw(img, 0, 0, 0, 1, 1, lume.round(img:getWidth()/2), img:getHeight())
+                if bag.id == lootBags.client.closest.id and lootBags.client.closest.dist < 30 then
+                    local img = gfx.ui.bag
+                    love.graphics.push()
+                    love.graphics.translate(-lume.round(img:getWidth()/2), -img:getHeight() - 20)
+                    love.graphics.draw(img, 0, 0)
+                    local bmx = mx - (lume.round(bag.x) - lume.round(img:getWidth()/2))
+                    local bmy = my - (lume.round(bag.y) - img:getHeight() - 20)
+                    for _, slot in ipairs(lootBags.client.slots) do
+                        if bmx >= slot.x and bmx <= slot.x + slot.w
+                        and bmy >= slot.y and bmy <= slot.y + slot.h then
+                            love.graphics.setColor(1, 1, 1, 0.8)
+                        else
+                            love.graphics.setColor(1, 1, 1, 0.2)
+                        end
+                        love.graphics.rectangle('fill', slot.x, slot.y, slot.w, slot.h)
+                    end
+                    love.graphics.setColor(1, 0, 0, 0.4)
+                    love.graphics.rectangle('fill', bmx, bmy, 2, 2)
+                    love.graphics.pop()
+                end
+                love.graphics.pop()
+            end,
+            y = bag.y
+        }
     end
 end
diff --git a/main.lua b/main.lua
index bafe051..99866a5 100644
--- a/main.lua
+++ b/main.lua
@@ -12,6 +12,7 @@ require 'client'
 require 'menu'
 require 'hud'
 require 'physics'
+require 'scene'
 require 'world'
 require 'player'
 require 'projectiles'
@@ -24,6 +25,7 @@ function love.load()
     gameState = 'menu'
     time = 0
     gameTime = 0
+    gcTimer = 10
     -- don't shoot if pressing ui
     uiMouseDown = false
     drawDebug = false
@@ -52,12 +54,14 @@ function setGameCanvas2x()
     local _color = {love.graphics.getColor()}
     love.graphics.setShader()
     love.graphics.setCanvas(canvases.game2x)
+    love.graphics.setBlendMode('alpha', 'premultiplied')
     love.graphics.setColor(1, 1, 1)
     love.graphics.push()
     love.graphics.origin()
     love.graphics.draw(canvases.game, 0, 0, 0, 2, 2)
     love.graphics.pop()
     love.graphics.setCanvas(canvases.game)
+    love.graphics.setBlendMode('alpha')
     love.graphics.clear()
     love.graphics.setCanvas(canvases.game2x)
     love.graphics.setShader(_shader)
@@ -74,6 +78,11 @@ function love.update(dt)
         client.update(dt)
     end
     menu.update(dt)
+    gcTimer = gcTimer - dt
+    if gcTimer < 0 then
+        collectgarbage()
+        gcTimer = 10
+    end
 end
 
 function love.mousepressed(x, y, btn, isTouch)
@@ -139,6 +148,8 @@ end
 
 function love.draw()
     local mx, my = window2game(love.mouse.getPosition())
+    mx, my = lume.round(mx), lume.round(my)
+    love.graphics.setBlendMode('alpha')
     love.graphics.setCanvas(canvases.game2x)
     love.graphics.clear()
     love.graphics.setCanvas(canvases.game)
@@ -152,6 +163,9 @@ function love.draw()
         projectiles.client.draw()
         player.draw()
 
+        scene.draw()
+        scene.reset()
+
         if drawDebug then
             if server.running then
                 local serverBodies = physics.server.world:getBodies()
@@ -177,7 +191,7 @@ function love.draw()
         chat.draw()
 
         love.graphics.setColor(1, 1, 1)
-        love.graphics.draw(gfx.cursors.main, lume.round(mx), lume.round(my), 0, 1, 1, 0, 0) -- hotspot 0, 0
+        love.graphics.draw(gfx.cursors.main, mx, my, 0, 1, 1, 0, 0) -- hotspot 0, 0
     end
 
     menu.draw()
@@ -185,6 +199,7 @@ function love.draw()
     -- draw game on game2x
     setGameCanvas2x()
     love.graphics.setCanvas()
+    love.graphics.setBlendMode('alpha', 'premultiplied')
     love.graphics.clear(0, 0, 0)
     love.graphics.setColor(1, 1, 1)
     love.graphics.draw(canvases.game2x, ssx/2-gameScale*gsx/2, ssy/2-gameScale*gsy/2, 0, gameScale/2, gameScale/2)
diff --git a/menu.lua b/menu.lua
index 04440da..75c66d8 100644
--- a/menu.lua
+++ b/menu.lua
@@ -288,6 +288,7 @@ end
 
 function menu.mousepressed(mx, my, btn)
     mx, my = window2game(mx, my)
+    mx, my = lume.round(mx), lume.round(my)
     if gameState == 'menu' then
         menu.activeInput = nil
         for _, v in pairs(menu.buttons[menu.state] or {}) do
@@ -363,7 +364,7 @@ end
 function menu.draw()
     if gameState == 'menu' then
         local mx, my = window2game(love.mouse.getPosition())
-
+        mx, my = lume.round(mx), lume.round(my)
         if menu.state == 'main' then
             love.graphics.setColor(1, 1, 1)
             local logoFrameIdx = math.floor(menu.logoAnimTimer*12) % #anims.logo.quads + 1
diff --git a/player.lua b/player.lua
index 0fe2a53..b206cac 100644
--- a/player.lua
+++ b/player.lua
@@ -59,6 +59,7 @@ end
 
 function player.swing()
     local mx, my = window2game(love.mouse.getPosition())
+    mx, my = lume.round(mx), lume.round(my)
     player.direction = mx < gsx/2 and -1 or 1
     player.swinging = true
     player.swingTimer = 0
@@ -77,6 +78,7 @@ end
 
 function player.update(dt)
     local mx, my = window2game(love.mouse.getPosition())
+    mx, my = lume.round(mx), lume.round(my)
 
     if not chat.active then
         local dx, dy = 0, 0
@@ -133,30 +135,105 @@ function player.mousereleased(x, y, btn)
 end
 
 function player.draw()
-    local _canvas = love.graphics.getCanvas()
-    local _shader = love.graphics.getShader()
 
     -- other players
 
     for _, v in pairs(client.currentState.players) do
         -- or debugger.show
         if v.id ~= player.id then
+            scene.add{
+                draw = function()
+                    local _canvas = love.graphics.getCanvas()
+                    local _shader = love.graphics.getShader()
+                    -- shadow
+                    love.graphics.setColor(0, 0, 0, 0.2)
+                    local shadowWidth = 5
+                    love.graphics.ellipse('fill', lume.round(v.x), lume.round(v.y), shadowWidth, 2)
+
+                    -- player
+                    love.graphics.setCanvas(canvases.tempGame)
+                    love.graphics.setShader()
+                    love.graphics.clear()
+                    love.graphics.setColor(1, 1, 1)
+                    local quad = anims.player.swing.quads[1]
+                    local _, _, w, h = quad:getViewport()
+                    love.graphics.draw(anims.player.swing.sheet, quad,
+                        lume.round(v.x), lume.round(v.y),
+                        0, 1, 1,
+                        23, h)
+
+                    -- outline
+                    love.graphics.setCanvas(_canvas)
+                    love.graphics.setShader(shaders.outline)
+                    love.graphics.setColor(1, 1, 1)
+                    love.graphics.push()
+                    love.graphics.origin()
+                    shaders.outline:send('stepSize', {
+                        1/canvases.tempGame:getWidth(),
+                        1/canvases.tempGame:getHeight()
+                    })
+                    love.graphics.draw(canvases.tempGame, 0, 0)
+                    love.graphics.pop()
+                    love.graphics.setShader(_shader)
+
+                    -- name
+                    local font = fonts.c17
+                    love.graphics.setFont(font)
+                    text.printSmall(v.name, lume.round(v.x) - font:getWidth(v.name)/4, lume.round(v.y) - 40)
+                end,
+                y = v.y
+            }
+        end
+    end
+
+    -- local player
+
+    local px, py = player.body:getPosition()
+    local xv, yv = player.body:getLinearVelocity()
+    local vd = math.sqrt(xv^2 + yv^2)
+
+    scene.add{
+        draw = function()
+            local _canvas = love.graphics.getCanvas()
+            local _shader = love.graphics.getShader()
             -- shadow
             love.graphics.setColor(0, 0, 0, 0.2)
-            local shadowWidth = 5
-            love.graphics.ellipse('fill', lume.round(v.x), lume.round(v.y), shadowWidth, 2)
+            local walkFrameIdx = math.floor(player.walkTimer*12) % #anims.player.walk.quads + 1
+            local shadowWidth = ({6, 5, 4, 5, 5})[walkFrameIdx]
+            if player.swinging or vd < 10 then shadowWidth = 6 end
+            love.graphics.ellipse('fill', lume.round(px), lume.round(py), shadowWidth, 2)
 
             -- player
             love.graphics.setCanvas(canvases.tempGame)
             love.graphics.setShader()
             love.graphics.clear()
             love.graphics.setColor(1, 1, 1)
-            local quad = anims.player.swing.quads[1]
-            local _, _, w, h = quad:getViewport()
-            love.graphics.draw(anims.player.swing.sheet, quad,
-                lume.round(v.x), lume.round(v.y),
-                0, 1, 1,
-                23, h)
+            if player.swinging then
+                local frameIdx = math.floor(player.swingTimer*12) + 1
+                frameIdx = lume.clamp(frameIdx, 1, 5)
+                local quad = anims.player.swing.quads[frameIdx]
+                local _, _, w, h = quad:getViewport()
+                love.graphics.draw(anims.player.swing.sheet, quad,
+                    lume.round(px), lume.round(py),
+                    0, player.direction, 1,
+                    23, h)
+            else
+                if vd < 10 then
+                    local quad = anims.player.swing.quads[1]
+                    local _, _, w, h = quad:getViewport()
+                    love.graphics.draw(anims.player.swing.sheet, quad,
+                        lume.round(px), lume.round(py),
+                        0, player.direction, 1,
+                        23, h)
+                else
+                    local quad = anims.player.walk.quads[walkFrameIdx]
+                    local _, _, w, h = quad:getViewport()
+                    love.graphics.draw(anims.player.walk.sheet, quad,
+                        lume.round(px), lume.round(py),
+                        0, player.direction, 1,
+                        8, h)
+                end
+            end
 
             -- outline
             love.graphics.setCanvas(_canvas)
@@ -175,77 +252,14 @@ function player.draw()
             -- name
             local font = fonts.c17
             love.graphics.setFont(font)
-            text.printSmall(v.name, lume.round(v.x) - font:getWidth(v.name)/4, lume.round(v.y) - 40)
-        end
-    end
-
-    -- local player
-
-    local px, py = player.body:getPosition()
-    local xv, yv = player.body:getLinearVelocity()
-    local vd = math.sqrt(xv^2 + yv^2)
+            text.printSmall(player.name, lume.round(px) - font:getWidth(player.name)/4, lume.round(py) - 40)
 
-    -- shadow
-    love.graphics.setColor(0, 0, 0, 0.2)
-    local walkFrameIdx = math.floor(player.walkTimer*12) % #anims.player.walk.quads + 1
-    local shadowWidth = ({6, 5, 4, 5, 5})[walkFrameIdx]
-    if player.swinging or vd < 10 then shadowWidth = 6 end
-    love.graphics.ellipse('fill', lume.round(px), lume.round(py), shadowWidth, 2)
-
-    -- player
-    love.graphics.setCanvas(canvases.tempGame)
-    love.graphics.setShader()
-    love.graphics.clear()
-    love.graphics.setColor(1, 1, 1)
-    if player.swinging then
-        local frameIdx = math.floor(player.swingTimer*12) + 1
-        frameIdx = lume.clamp(frameIdx, 1, 5)
-        local quad = anims.player.swing.quads[frameIdx]
-        local _, _, w, h = quad:getViewport()
-        love.graphics.draw(anims.player.swing.sheet, quad,
-            lume.round(px), lume.round(py),
-            0, player.direction, 1,
-            23, h)
-    else
-        if vd < 10 then
-            local quad = anims.player.swing.quads[1]
-            local _, _, w, h = quad:getViewport()
-            love.graphics.draw(anims.player.swing.sheet, quad,
-                lume.round(px), lume.round(py),
-                0, player.direction, 1,
-                23, h)
-        else
-            local quad = anims.player.walk.quads[walkFrameIdx]
-            local _, _, w, h = quad:getViewport()
-            love.graphics.draw(anims.player.walk.sheet, quad,
-                lume.round(px), lume.round(py),
-                0, player.direction, 1,
-                8, h)
-        end
-    end
-
-    -- outline
-    love.graphics.setCanvas(_canvas)
-    love.graphics.setShader(shaders.outline)
-    love.graphics.setColor(1, 1, 1)
-    love.graphics.push()
-    love.graphics.origin()
-    shaders.outline:send('stepSize', {
-        1/canvases.tempGame:getWidth(),
-        1/canvases.tempGame:getHeight()
-    })
-    love.graphics.draw(canvases.tempGame, 0, 0)
-    love.graphics.pop()
-    love.graphics.setShader(_shader)
-
-    -- name
-    local font = fonts.c17
-    love.graphics.setFont(font)
-    text.printSmall(player.name, lume.round(px) - font:getWidth(player.name)/4, lume.round(py) - 40)
-
-    if drawDebug then
-        love.graphics.setColor(1, 0, 0, 0.5)
-        love.graphics.circle('fill',
-            lume.round(px), lume.round(py), player.shape:getRadius())
-    end
+            if drawDebug then
+                love.graphics.setColor(1, 0, 0, 0.5)
+                love.graphics.circle('fill',
+                    lume.round(px), lume.round(py), player.shape:getRadius())
+            end
+        end,
+        y = py
+    }
 end
diff --git a/projectiles.lua b/projectiles.lua
index dc93784..2640f9b 100644
--- a/projectiles.lua
+++ b/projectiles.lua
@@ -95,35 +95,40 @@ end
 
 
 function projectiles.client.draw()
-    local _canvas = love.graphics.getCanvas()
-    local _shader = love.graphics.getShader()
     for _, v in pairs(client.currentState.projectiles) do
         if v.startedMoving then
-            love.graphics.setCanvas(canvases.tempGame)
-            love.graphics.setShader()
-            love.graphics.clear()
-            love.graphics.setColor(192/255, 192/255, 192/255)
-            love.graphics.push()
-            love.graphics.translate(lume.round(v.x), lume.round(v.y))
-            love.graphics.rotate(-v.angle)
-            for _, poly in pairs(v.polys) do
-                love.graphics.polygon('fill', poly)
-            end
-            love.graphics.pop()
+            scene.add{
+                draw = function()
+                    local _canvas = love.graphics.getCanvas()
+                    local _shader = love.graphics.getShader()
+                    love.graphics.setCanvas(canvases.tempGame)
+                    love.graphics.setShader()
+                    love.graphics.clear()
+                    love.graphics.setColor(192/255, 192/255, 192/255)
+                    love.graphics.push()
+                    love.graphics.translate(lume.round(v.x), lume.round(v.y))
+                    love.graphics.rotate(-v.angle)
+                    for _, poly in pairs(v.polys) do
+                        love.graphics.polygon('fill', poly)
+                    end
+                    love.graphics.pop()
 
-            -- outline
-            love.graphics.setCanvas(_canvas)
-            love.graphics.setShader(shaders.outline)
-            love.graphics.setColor(1, 1, 1)
-            love.graphics.push()
-            love.graphics.origin()
-            shaders.outline:send('stepSize', {
-                1/canvases.tempGame:getWidth(),
-                1/canvases.tempGame:getHeight()
-            })
-            love.graphics.draw(canvases.tempGame, 0, 0)
-            love.graphics.pop()
-            love.graphics.setShader(_shader)
+                    -- outline
+                    love.graphics.setCanvas(_canvas)
+                    love.graphics.setShader(shaders.outline)
+                    love.graphics.setColor(1, 1, 1)
+                    love.graphics.push()
+                    love.graphics.origin()
+                    shaders.outline:send('stepSize', {
+                        1/canvases.tempGame:getWidth(),
+                        1/canvases.tempGame:getHeight()
+                    })
+                    love.graphics.draw(canvases.tempGame, 0, 0)
+                    love.graphics.pop()
+                    love.graphics.setShader(_shader)
+                end,
+                y = v.y
+            }
         end
     end
 end
diff --git a/scene.lua b/scene.lua
new file mode 100644
index 0000000..2e70bd2
--- /dev/null
+++ b/scene.lua
@@ -0,0 +1,39 @@
+
+scene = {
+    layers = {}
+}
+
+-- todo: persistent scene: much faster sorting
+
+function scene.reset()
+    scene.layers = {}
+end
+
+-- t = {draw=_, y=_, layer=_, type=_}
+function scene.add(t)
+    if t.layer == nil then t.layer = 1 end
+    if scene.layers[t.layer] == nil then scene.layers[t.layer] = {} end
+    table.insert(scene.layers[t.layer], t)
+end
+
+function scene.draw()
+    local layers = {}
+    for k, v in pairs(scene.layers) do
+        table.insert(layers, {k=k, v=v})
+    end
+    layers = isort(layers, 'k')
+    for _, layer in ipairs(layers) do
+        local sorted = isort(layer.v, function(a, b)
+            if a.type == 'entityBody' and b.type == 'entityHP' then
+                return true
+            elseif a.type == 'entityHP' and b.type == 'entityBody' then
+                return false
+            else
+                return a.y < b.y
+            end
+        end)
+        for _, v in pairs(sorted) do
+            v.draw()
+        end
+    end
+end
diff --git a/utils.lua b/utils.lua
index 84944df..0859fe5 100644
--- a/utils.lua
+++ b/utils.lua
@@ -45,3 +45,27 @@ ease = {
 function buildName(name, postfix)
 	return name .. (postfix ~= 0 and '(' .. postfix .. ')' or '')
 end
+
+function isort(_t, comp, rev)
+	if comp == nil then
+		comp = function(a, b) return a < b end
+	elseif type(comp) ~= 'function' then
+		local k = comp
+		comp = function(a, b) return a[k] < b[k] end
+	end
+	if rev then
+		_comp = comp
+		comp = function(a, b) return not _comp(a, b) end
+	end
+	local t = {}
+	for i=1, #_t do
+		local v = _t[i]
+		local j = i - 1
+		while j > 0 and not comp(t[j], v) do
+			t[j+1] = t[j]
+			j = j - 1
+		end
+		t[j+1] = v
+	end
+	return t
+end