--checkers by rnd, 1.5 hr
if not init then init=true
	spos = self.spawnpos()
	self.listen_punch(self.pos()) -- attach punch listener
	sizex = 8; sizez= 8
	
	gamepieces = {
		{ -- player1: regular piece, queen
			"basic_robot:buttonFFFF80","basic_robot:buttonFF8080"
		},
		{ -- player2
			"basic_robot:button80FF80","basic_robot:button8080FF"
		}
	}
	show_mark = function(pos)
		minetest.add_particle(
		{
			pos = pos,
			expirationtime = 5,
			velocity = {x=0, y=0,z=0},
			size = 18,
			texture = "default_apple.png",
			acceleration = {x=0,y=0,z=0},
			collisiondetection = true,
			collision_removal = true,			
		}
		)
	end
		
	build_game = function()
		for i = 1,sizez do
			for j = 1,2 do
				minetest.swap_node({x=spos.x+j,y=spos.y,z=spos.z+i},{name = "basic_robot:button_131"})
				minetest.swap_node({x=spos.x+j,y=spos.y+1,z=spos.z+i},{name = "air"})
			end
			minetest.swap_node({x=spos.x+3,y=spos.y,z=spos.z+i},{name = "basic_robot:button_".. (48+i), param2 = 3})
		end
		for i = 1,sizex do
			minetest.swap_node({x=spos.x+3+i,y=spos.y,z=spos.z},{name = "basic_robot:button_".. (64+i)})
			minetest.swap_node({x=spos.x+3+i,y=spos.y,z=spos.z+sizez+1},{name = "basic_robot:button_".. (64+i), param2 = 2})
		end
		local white = true;
		for i = 1,sizex do
			for j = 1,sizez do
				if white then
					minetest.swap_node({x=spos.x+3+i,y=spos.y,z=spos.z+j},{name = "basic_robot:button_0"})
				else
					minetest.swap_node({x=spos.x+3+i,y=spos.y,z=spos.z+j},{name = "basic_robot:button808080"})
				end
				white = not white
				minetest.swap_node({x=spos.x+3+i,y=spos.y+1,z=spos.z+j},{name = "air"})
			end
			white = not white
		end
		minetest.swap_node({x=spos.x+1,y=spos.y+1,z=spos.z+1},{name = gamepieces[1][1]})
		minetest.swap_node({x=spos.x+1,y=spos.y+2,z=spos.z+1},{name = gamepieces[1][2]})
		
		minetest.swap_node({x=spos.x+1,y=spos.y+1,z=spos.z+sizez},{name = gamepieces[2][1]})
		minetest.swap_node({x=spos.x+1,y=spos.y+2,z=spos.z+sizez},{name = gamepieces[2][2]})
		
		for i=1,sizex,2 do
			minetest.swap_node({x=spos.x+4+i,y=spos.y+1,z=spos.z+1},{name = gamepieces[1][1]})
			minetest.swap_node({x=spos.x+3+i,y=spos.y+1,z=spos.z+2},{name = gamepieces[1][1]})
			
			minetest.swap_node({x=spos.x+4+i,y=spos.y+1,z=spos.z+sizez-1},{name = gamepieces[2][1]})
			minetest.swap_node({x=spos.x+3+i,y=spos.y+1,z=spos.z+sizez},{name = gamepieces[2][1]})
		end
	end
	
	msgs = {1} --{idx, msg1, msg2,msg3, msg4, msg5}; -- up to 5 ingame messages displayed
	add_msg = function(text)
		local idx = msgs[1] or 1; 
		msgs[idx+1] = text;idx = idx+1; if idx>5 then idx = 1 end msgs[1] = idx
	end
	show_msgs =  function() -- last message on top
		local out = {}; local idx = msgs[1] or 1;
		for i = idx,2,-1 do out[#out+1] = msgs[i] or "" end 
		for i = 6, idx+1,-1 do out[#out+1] = msgs[i] or "" end 
		self.label(table.concat(out,"\n")) 
	end
	
	build_game()
	punchpos = nil; -- pos of last punched piece
	step = 0;
	self.label("checkers\npunch piece then punch board to move\n"..
	"RULES\n\n1. move only diagonal and forward. capture pieces by jumping over them.\nif you can capture you must\n"..
	"2. once you reach end of board you get king. it can move backward too"	
	)
end

event = keyboard.get()


if event then
	--self.label(serialize(event))
	if event.y==spos.y+1 then -- piece was punched to be moved
		punchpos = {x=event.x,y=event.y,z=event.z}
	elseif event.y==spos.y and event.x~=spos.x+3 then -- board was punched
		if not punchpos then return end
		
		step = step+1
		local x1 = punchpos.x-spos.x-3; local z1 = punchpos.z-spos.z
		local x2 = event.x-spos.x-3; local z2 = event.z-spos.z
		add_msg(minetest.colorize("red","MOVE " .. step) .. ": " .. event.puncher .. " " .. string.char(64+x1) .. z1 .. " to " .. string.char(64+x2) .. z2); show_msgs()
		
		local nodename = minetest.get_node(punchpos).name
		minetest.swap_node(punchpos,{name = "air"})
		show_mark(punchpos)
		
		-- promotion of pieces to queen when reaching the opposite side
		if nodename == gamepieces[1][1] and event.z==spos.z+sizez and event.x>spos.x+3 then 
			nodename = gamepieces[1][2]
		elseif nodename == gamepieces[2][1] and event.z==spos.z+1 and event.x>spos.x+3 then 
			nodename = gamepieces[2][2]
		end
		
		minetest.swap_node({x=event.x,y=event.y+1,z=event.z},{name = nodename})
		show_mark({x=event.x,y=event.y+2,z=event.z})
		punchpos = nil
	end
end