flappy.p8

pico-8 cartridge // http://www.pico-8.com
version 18
__lua__
-- this is called automatically
-- one time when the game starts
-- but we'll call it again later
-- to start the game over
function _init()
	-- later, when the game is over
	-- we'll call this functiom
	-- again to set this value back
	-- to false
	game_over=false
	-- how fast the player
	-- accelerates downwards.
	-- bigger means more gravity.
	gravity=0.2
	-- how fast the player travels
	-- towards the obstacles, or
	-- really, how fast the obstacles
	-- travel towards the player
	-- since the player's x position
	-- never changes
	speed=2
	-- player jump speed. bigger
	-- means higher jumps.
	jump=2
	-- this sets the initial values
	-- for the player
	make_player()
	-- this creates a new pole
	-- coming towards the player.
	-- the first one gets created
	-- here, but others will be
	-- created as the pole falls
	-- off the left side of the
	-- screen
	make_pole()
	-- play the music track
	music(0)
end

-- this is called automatically
-- 30 times per second. used to
-- update your game "state"
function _update()
	if (not game_over) then
		-- only update positions of
		-- things if the game is not
		-- over
		move_player()
		move_pole()
		check_hit()
	elseif (btnp(5)) then
		-- this restarts the game
		_init()
	end
end

-- this is called automatically
-- 30 times per second, like the
-- _update function, but this is
-- where you actually draw things
function _draw()
	-- clear the screen, otherwise
	-- stuff from the last frame
	-- would still be displayed.
	-- the "1" argument is the color
	-- blue
	cls(1)
	draw_pole()
	draw_player()
	
	if (game_over) then
		print("game over", 46, 60, 7)
		print("press ❎ to start over", 22, 68, 7)
	end
end

-->8
function make_player()
	-- this makes an empty "table"
	-- to represent our player.
	player={}
	-- x position on screen
	player.x=12
	-- y position on screen.
	-- 60 is right in the middle.
	player.y=60
	-- dy stands for "delta y"
	-- "delta" means "change" so 
	-- this is the current change
	-- in y. we set this to "-jump"
	-- so the player is initially
	-- jumping.
	player.dy=-jump
	-- index of the sprites in the
	-- sprite sheet. change tabs
	-- to see all the sprites.
	player.flap=6
	player.glide=7
end

-- called from _update()
function move_player()
	-- since gravity is an 
	-- "acceleration" force, the "dy"
	-- value increases every frame
	-- so that the player falls
	-- faster and faster
	player.dy += gravity

	if (btnp(2)) then
		-- if the up button (2) is 
		-- pressed, cancel out the fall
		-- speed by resetting the "dy"
		-- to the "jump" force. using
		-- a negative here because
		-- the "y" axis is top to bottom
		player.dy = -jump
		-- play the "flap" sound fx
		sfx(1)
	end

	-- add the change in y (dy) to
	-- the player's current y
	player.y += player.dy
end

-- called from _draw()
function draw_player()
	-- if "dy" is negative, the
	-- player is moving upwards
	-- and the bird has "flapped".
	-- so draw the "flap" sprite.
	-- otherwise, draw the "glide"
	-- sprite
	if (player.dy < 0) then
		spr(player.flap, player.x, player.y)
	else
		spr(player.glide, player.x, player.y)
	end
end

-- called from _update()
function check_hit()
	-- this checks if the player is
	-- colliding with the top or
	-- bottom of the screen
	if (player.y < 0 or player.y+8 > 128) then
		end_game()
	
	-- this checks if the player is
	-- colliding with the pole.
	-- 
	-- the outer "if" checks if the
	-- player's x position is inside
	-- the pole's x position and
	-- width.
	--
	-- if that succeeds, we need to
	-- check if the player is inside
	-- the "hole"
	elseif (player.x > pole.x-8 and player.x < pole.x+pole.width) then
		if (player.y < pole.hole_y or player.y+8 > pole.hole_y+pole.hole_size) then
			end_game()
		end
	end
end

function end_game()
	game_over=true
	-- play the dying sound effect.
	-- tweak this in the sounds
	-- tab.
	sfx(0)
	-- stop the music
	music(-1)
end

-->8
-- create a new pole
function make_pole()
	-- make an empty "table"
	pole={}
	-- pole's width in pixels
	pole.width=16
	-- the width of the opening
	-- the player must pass through
	-- in pixels
	pole.hole_size=40
	-- starting the pole off the
	-- right edge of the screen 
	pole.x=128
	-- set a random y position for
	-- the hole.
	-- "rnd" returns a number between
	-- zero and the provided value.
	pole.hole_y=rnd(128-pole.hole_size)
end

-- called from _update()
function move_pole()
	-- moves the pole to the left
	-- by the "speed" amount
	pole.x -= speed

	-- if pole has moved off the
	-- left edge of the screen,
	-- make a new pole	
	if (pole.x <= -pole.width) then
		make_pole()
	end
end

function draw_pole()
	-- draw the top part of the pole
	-- as a rectangle.
	-- this function takes arguments
	-- for: x,y,x,y,color
	-- there are great docs on the
	-- internet for all the kinds
	-- of drawing calls you can
	-- make.
	rectfill(pole.x, 0, pole.x+pole.width, pole.hole_y, 3)
	-- draw the bottom part of the
	-- pole as a rectangle.
	rectfill(pole.x, pole.hole_y+pole.hole_size, pole.x+pole.width, 128, 3)
end

__gfx__
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__sfx__
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__music__
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