main.lua

Rain = {
    x = 0,
    y = 0,
    width = 0,
    height = 0,
    opacity = 0,
    speed = 0
}

function Rain:new(o, x, speed, opacity)
    o = o or {}
    setmetatable(o, self)
    self.__index = self
    self.x = x or 1
    self.y = 1

    self.width = RAIN_WIDTH
    self.height = RAIN_HEIGHT

    self.opacity = opacity or 1
    self.speed = speed or 100

    return o
end

function CAL_VARS()

    DENSITY = 0.3

    WIDTH_OF_WINDOW = love.graphics.getWidth()
    HEIGHT_OF_WINDOW = love.graphics.getHeight()

    RAIN_WIDTH = WIDTH_OF_WINDOW / 266
    RAIN_HEIGHT = HEIGHT_OF_WINDOW / 37

    NUM_OF_RAIN_DROPS = (WIDTH_OF_WINDOW * HEIGHT_OF_WINDOW) / (RAIN_HEIGHT * RAIN_WIDTH) * DENSITY

    TOP_SPEED = HEIGHT_OF_WINDOW
    LOWEST_SPEED = WIDTH_OF_WINDOW
end

function CREATE_RAIN_DROPS()
    RAIN_DROPS = {}
    for _ = 1, NUM_OF_RAIN_DROPS do
        local r = Rain:new {
            x = math.random(WIDTH_OF_WINDOW),
            speed = math.random(LOWEST_SPEED, TOP_SPEED),
            opacity = math.random()
        }

        table.insert(RAIN_DROPS, r)

        for _ = 1, math.floor((10 - r.opacity * 10) / 2) do
            table.insert(RAIN_DROPS, Rain:new {
                x = math.random(WIDTH_OF_WINDOW),
                speed = r.speed,
                opacity = r.opacity
            })
            NUM_OF_RAIN_DROPS = NUM_OF_RAIN_DROPS + 1
        end
    end
end

function love.load()


    CAL_VARS()

    CREATE_RAIN_DROPS()

    love.graphics.setBackgroundColor(230, 230, 250)

    R = {}
end

function love.resize()
    CAL_VARS()
    CREATE_RAIN_DROPS()
end

function love.keypressed(key)
    if key == 'q' then
        love.event.quit(0)
    end
end

function love.update(dt)
    for i = 1, #RAIN_DROPS do
        local r = RAIN_DROPS[i]
        if r == nil then love.event.quit(0) else
            if r.y < HEIGHT_OF_WINDOW then
                r.y = r.y + (r.speed * dt)
            else
                r.y = 0
                r.x = math.random(WIDTH_OF_WINDOW)
                r.opacity = math.random()
                r.speed = math.random(LOWEST_SPEED, TOP_SPEED) * r.opacity
                r.width = RAIN_WIDTH * r.opacity
                r.heigth = RAIN_HEIGHT * r.opacity
            end
        end
    end
end

function love.draw()
    for i = 1, NUM_OF_RAIN_DROPS do
        R = RAIN_DROPS[i]
        if R ~= nil then
            love.graphics.setColor(128 / 255, 43 / 255, 226 / 255, R.opacity)
            --love.graphics.setColor(255 / 255, 255 / 255, 255 / 255, R.opacity)
            love.graphics.rectangle('fill', R.x, R.y, R.width, R.height)
        end
    end
end