# Lua and the LOVE Game Framework #

(January 2017)

LOVE is a multi-platform game framework.
Write games in Lua (Lua 5.1).

Debian has a `love` package, or download from https://love2d.org/#download.

Put games files in a directory.
The root of the directory should contain the `main.lua` file.
Games can be packaged into `mygame.love` files or run from the directory.
Run a game like:

	$ love /home/me/gamedir/
	$ love /home/me/gamepackage.love

`main.lua` for `helloworld/`:

	function love.draw()
		love.graphics.print("Hello World", 400, 300)
	end

## Callback Functions ##

A callback function works backwards.
With a non-callback function, we call Lua or LOVE code and expect it to do something.
With a callback function, we write code that LOVE calls.
This acts as a structural tool.

love.load()
LOVE always calls our `love.load` function when first starting the game, so `love.load` is a reliable place to put our initialization stuff.

love.update()
LOVE continuously calls `love.update`.

	function love.update(dt)
	   if love.keyboard.isDown("up") then
		  num = num + 100 * dt -- this would increment num by 100 per second
	   end
	end

love.draw()
What LOVE continuously calls update graphics.

	function love.draw()
	   love.graphics.draw(image, imgx, imgy)
	   love.graphics.print("Click and drag the cake around or use the arrow keys", 10, 10)
	end

love.mousepressed()
LOVE calls this whenever the user presses a mouse button.
(Available since LÖVE 0.10.0)

	function love.mousepressed(x, y, button, istouch)
	   if button == 1 then
		  imgx = x -- move image to where mouse clicked
		  imgy = y
	   end
	end


love.mousereleased()
LOVE calls this whenever the user releases a mouse button.
(Available since LÖVE 0.10.0)

	function love.mousereleased(x, y, button, istouch)
	   if button == 1 then
		  fireSlingshot(x,y) -- this totally awesome custom function is defined elsewhere
	   end
	end

love.keypressed()
LOVE calls this everytime a KeyConstant is pressed.
See https://love2d.org/wiki/KeyConstant

	function love.keypressed(key)
	   if key == 'b' then
		  text = "The B key was pressed."
	   elseif key == 'a' then
		  a_down = true
	   end
	end

love.keyreleased()
LOVE calls this when the user releases a keyboard key.

	function love.keyreleased(key)
	   if key == 'b' then
		  text = "The B key was released."
	   elseif key == 'a' then
		  a_down = false
	   end
	end

love.focus()
LOVE callse `love.focus` when the user focuses or de-focuses the game window.

	function love.focus(f)
	  if not f then
		print("LOST FOCUS")
	  else
		print("GAINED FOCUS")
	  end
	end

love.quit()
LOVE calls this when the user clicks the window's CLOSE button.

	function love.quit()
	  print("Thanks for playing! Come back soon!")
	end


## Packaging ##

Package games.

## Links ##

https://love2d.org/wiki/Main_Page
https://love2d.org/wiki/Tutorial:Callback_Functions