[PICO8] Animation Demo.

 buttons = {
   left  = 0,
   right = 1,
   up    = 2,
   down  = 3,
   z     = 4,
   x     = 5,
 }
-- game
 -- 1,5  : game clocks
 gameclockmax = 5
 -- 6,20+: anim clocks
 animclockstart = 6
 animations = {
  -- animation blocks (index),
  -- animation size   (w,h),
  -- animation length (blocks),
  -- animation speed  (sec)
  -- animation flips  (x,y)
  p_up    = {7,1,1,3,0.12},
  p_down  = {1,1,1,3,0.12},
  p_left  = {4,1,1,3,0.12,true},
  p_right = {4,1,1,3,0.12},
  bat_fly = {20,1,1,3,0.15},
 }

 camx = 0
 camy = 0
-- draws debug text
 debug = false
-- create player, get animations working

function smallprint(txt,x,y,col)
  local font = {
    ['a'] = 225,
    ['b'] = 226,
    ['c'] = 227,
    ['d'] = 228,
    ['e'] = 229,
    ['f'] = 230,
    ['g'] = 231,
    ['h'] = 232,
    ['i'] = 233,
    ['j'] = 234,
    ['k'] = 235,
    ['l'] = 236,
    ['m'] = 237,
    ['n'] = 238,
    ['o'] = 239,
    ['p'] = 240,
    ['q'] = 241,
    ['r'] = 242,
    ['s'] = 243,
    ['t'] = 244,
    ['u'] = 245,
    ['v'] = 246,
    ['w'] = 247,
    ['x'] = 248,
    ['y'] = 249,
    ['z'] = 250,
  }
  for i = 1, #txt do
     local sprite = font[sub(txt,i,i)]
     if(sprite != nil)then
       -- switch sprite colors with new ones
       pal(7,col)
       spr(sprite,x+((i-1)*6),y)
       pal()
     else
       print(sub(txt,i,i),x+((i-1)*6),y)
     end
  end
end

function _init()
 cls()
 -- game vars
 clocks = {}
 player = {
   x = 63,
   y = 63,
   xvel = 0,
   yvel = 0,
   fric = 3,
   spd  = 0.75,
   damp = 1.5,
   width  = 4,
   height = 7,

   init = function(self)
     load_animation(animations.p_down,1)
     pause_animation(1)
   end,

   draw = function(self)
     play_animation(self.x,self.y,1,1)
   end,

   update = function(self)
      local moved = false
      if(btn(buttons.up))then
         moved = true
         self.yvel -= self.spd/self.damp
         load_animation(animations.p_up,1)
      end
      if(btn(buttons.down))then
         moved = true
         self.yvel += self.spd/self.damp
         load_animation(animations.p_down,1)
      end
      if(btn(buttons.left))then
         moved = true
         self.xvel -= self.spd/self.damp
         load_animation(animations.p_left,1)
      end
      if(btn(buttons.right))then
         moved = true
         self.xvel += self.spd/self.damp
         load_animation(animations.p_right,1)
      end
      -- friction
      if(not btn(buttons.left) and not btn(buttons.right))then
        self.xvel /= self.fric
      end
      if(not btn(buttons.up) and not btn(buttons.down))then
        self.yvel /= self.fric
      end

      if(self.xvel > self.spd) self.xvel = self.spd
      if(self.xvel < -self.spd) self.xvel = -self.spd
      if(self.yvel > self.spd) self.yvel = self.spd
      if(self.yvel < -self.spd) self.yvel = -self.spd

      if(not checksolid(self.x+self.xvel,self.y,self.width,self.height))then
         self.x += self.xvel
      else
         self.xvel = 0
      end

      if(not checksolid(self.x,self.y+self.yvel,self.width,self.height))then
         self.y += self.yvel
      else
         self.yvel = 0
      end


      if(moved)then
        if(animation_ispaused(1)) resume_animation(1,0.12)
      else
         pause_animation(1)
         setframe_animation(1,1)
      end

   end,

 }
 animations_active = {
   frames = {}
 }
 game_init()
end


colchxmin = 0
colchxmax = 0
colchymin = 0
colchymax = 0
function checksolid(x,y,w,h)
 -- loop through every pixel corresponding to a possible cell
 -- /8 used because pixel map is 8 pixels.
 -- example
 -- from x=10,y=12,w=4,h=7
 -- 10-4 = (6/8)+3.0 = 3,
 -- 10+4 = 14 + 0.5  = 14:
 -- 12-7 = 6/8 + 0.5 = 1,
 -- 12+7 = 19-0.5    = 18
 -- checks:
 -- (3, 14)/8 = 0.375, 1.75
 -- (1, 18)/8 = 0.125, 2.25
 colchxmin = flr((x-w/8)+3.0)/8
 colchxmax = flr((x+w)+0.5)/8
 colchymin = flr((y-h/8)+0.5)/8
 colchymax = flr((y+h)-0.5)/8
 for x=flr((x-w/8)+3.0),flr((x+w)+0.5) do  -- *8,-2.5+w
  for y=flr((y-h/8)+0.5),flr((y+h)-0.5) do -- *8,-1+h
   if fget(mget(x/8,y/8),1) then
     return true
   end
  end
 end
 return false
end

function load_animation(anim,slot)
 -- if we already have this animation, don't reset it!
  if(animations_active[slot] != anim) animations_active.frames[slot] = 1
  -- add animation to anim list
  animations_active[slot] = anim
  -- set frames
end

function animation_ispaused(slot)
   if( animations_active[slot] == nil) return false
   return animations_active[slot][5] == -1
end

function add_animation(anim)
  -- add animation to anim list
  animations_active[#animations_active+1] = anim
  -- set frames
  animations_active.frames[#animations_active.frames+1] = 1
  -- return where animation was loaded.
  return #animations_active
end

function unload_animation(slot)
  if(animations_active[slot] != nil)then
     -- use object here
     del(animations_active,animations_active[slot])
     -- because frames is a integeral value, use that just as is.
     del(animations_active.frames,slot)
  end
end

function play_animation(x,y,slot,loop)
  loop = loop or false
  -- animation structure in _init
  -- animation clock stored in clocks
  if(animations_active[slot] == nil)then
    -- animation not loaded!
    --print("no animation.",0,20,7)
    return false
  else
    -- load animation in
    anim = animations_active[slot]
  end
  -- pre-caution
  anim = anim or {0,0,0,0,0,0,0}
  local block, sizew,sizeh, length, speed, flipx, flipy = anim[1],anim[2],anim[3],anim[4],anim[5],anim[6],anim[7]
  -- make sure these are not nil!
  flipx = flipx or false
  flipy = flipy or false
  if(clocks[animclockstart+slot] == nil)then
     clocks[animclockstart+slot] = time()
  end
  if(speed != -1)then
   if( (time() - clocks[animclockstart+slot]) >= speed )then
     -- next frame
     if(animations_active.frames[slot] >= length)then
      -- loop frames are remove animation
      if(loop)then
       animations_active.frames[slot] = 1
      else
       unload_animation(slot)
       return true
      end
     else
      animations_active.frames[slot] += 1
      clocks[animclockstart+slot] = time()
     end
   end
  end
  -- draw animation
  spr(block+animations_active.frames[slot]-1,x,y,sizew,sizeh,flipx,flipy)
end

function pause_animation(slot)
   if(animations_active[slot] == nil) return false
   -- freeze animation clock
   animations_active[slot][5] = -1
   clocks[animclockstart+slot] = time()
end

function resume_animation(slot,spd)
   spd = spd or -1
   if(animations_active[slot] == nil) return false
   -- set animation clock
   animations_active[slot][5] = spd
   clocks[animclockstart+slot] = 0
end

function setframe_animation(slot,frame)
   if(animations_active.frames[slot] == nil) return false
   -- set animation clock
   animations_active.frames[slot] = frame
   clocks[animclockstart+slot] = 0
end


function game_init()
  -- fill screen with grass
  for y = 0, 32 do
     for x = 0, 32 do
       mset(x,y,10+flr(rnd(4)))
     end
  end
  -- 32 random blocks
  for i = 1, 32 do
   mset(flr(rnd(32)),flr(rnd(32)),14+flr(rnd(5)))
  end
  load_animation(animations.bat_fly,2)
  player:init()
end

function _draw()
 map(0,0,0,0,32,32)
 player:draw()
 play_animation(40,50,2,1)
 -- draw solids on-top of player.
 map(0,0,0,0,16,16,2)
 if(debug)then
  print("colx: (" ..colchxmin .. ", " .. colchxmax .. ")" ,0,0,7)
  print("coly: (" ..colchymin .. ", " .. colchymax .. ")" ,0,8,7)
  print("cell: " .. flr(player.x/8) .. ", " .. flr(player.y/8),0,16,7)
 else
  rectfill(camx,camy,127+camx,15+camy,0)
  print("pixel rpg demo",40+camx,10+camy,7)
  smallprint("welcome!",45+camx,0+camy,7)
 end

end



function _update60()
  player:update()
  camx = max(player.x-63,0)
  camy = max(player.y-63,0)
  if(camx > 127) camx = 127
  if(camy > 127) camy = 127
  -- cam change
  camer