start=1       --sprite index in the sheet or table
 frames=1      --number of frames in the loop
 frame=0       --current playing/starting frame
 spd = 0.1     --added to frame count each tick, higher is faster

 frtbl=nil,    -- if nil, use normal `start` and `frames` logic to loop through

 playing=true  --when true, frame increases by speed every time playspr is called
 loop = true   --if false stops when reaching end
 restfr=nil    --optional idle frame when not playing
 w=1           --width in sprite tiles
 h=1           --height in sprite tiles
 flpx=false    --flips the sprite horizontally
 flpy=false    --flips the sprite vertically

--fully optional variables, included for convenience:
 x=0
 y=0

--animated sprite functions
--by snjo
--
--create new sprite using aspr:
--myspr=aspr:new({start=16,frames=4})
--use anim() to draw and 
--progress animation
--use playspr() and stopspr()
--to freeze or unfreeze anim

function anim(s,x,y)
--s: an aspr, x/y: screen position
--draws a sprite and updates its animation

	--frame increases based on sprite width
	mult = s.frtbl and 1 or s.w
	local fr = s.start+(flr(s.frame)*mult)
	--if rest frame is defined, go to that when stopped
	if s.restfr and not s.playing then
		fr = s.restfr
	end
	flx,fly=s.flpx,s.flpy

	--anim frames in table:
	--this next section can be
	--removed if not used in game

	if s.frtbl then
		local t = s.frtbl[fr]
		if type(t)=="table" then
			 flx,fly = 1==t[2]&1,2==t[2]&2
			 usefr = t[1]
		else 
			 usefr = t
		end
	else
		usefr = fr
	end

	--draw to screen
	spr(usefr,x,y,s.w,s.h,flx,fly)
	--progress sprite's frame
	if s.playing then
		s.frame = (s.frame+s.spd)%s.frames
	end

	if not s.loop then
		if fr>=s.start+s.frames-1 then
			 stopspr(s)
		end 
	end
end

function playspr(s,rst)
--s: an aspr, rst:go to first frame?
	s.playing = true
	--if reset or sprite is on 
	--the rest frame
	--if s.frame == s.restfr or rst then
	if rst then
		s.frame = s.start
	end
end

function stopspr(s,rst)
--s: an aspr, rst:go to first frame?
	s.playing = false
	--if reset, go to start frame
	--if (rst) s.frame = 0
	if restfr then
			 s.frame = s.restfr
	elseif rst then
		s.frame = s.start
	end
end

function togglespr(s,rst)
--this function is optional
	if s.playing then
		stopspr(s,rst)
	else
		playspr(s,rst)
	end
end

--metatable definition

aspr={
--animated sprite
--to create a sprite: 
--myspr=aspr:new({start=16,frames=4})

	--required attributes:
	start=1, --sprite index in the sheet or table
	frames=1, --number of frames in the loop
	frame=0, --current playing/starting frame
	spd = 0.1, --added to frame count each tick, higher is faster

	--more attributes, can be trimmed with code change:
	frtbl=nil,
		--use frame table instead of count
		--each frame can itself a table
		--{frame,flip} where 1:x, 2:y
		-- 3:x and y flipped
		--example: frtbl(16,{16,1})
		--(second frame is flipped x)

	playing=true,--when true, frame increases by speed every time playspr is called
	loop = true,--if false stops when reaching end
	restfr=nil, --optional idle frame when not playing
	w=1, --width in sprite tiles
	h=1, --height in sprite tiles
	flpx=false, --flips the sprite horizontally
	flpy=false, --flips the sprite vertically

	--fully optional:
	x=0,
	y=0,

	--return the new sprite object
	new=function(self,t)
		return setmetatable(t or {},{__index=self})
	end
}