Why does my lua script get different values each time I run it?

Question

I have created a simple 2d scene in Love2D with a square that falls until it reaches a certain point and then stops. The problem is that the square stops at a slightly different point every time with no user input or modified code.

Here is my lua

function love.load()
    playY = 0
    playX = 10
    grav = 200
    speed = 100
end

function love.draw()
    --floor
    love.graphics.setColor(0,255,0,255)
    love.graphics.rectangle("fill", 0,465,800,150)
    --player
    love.graphics.setColor(255,255,0,255)
    love.graphics.rectangle("fill", playX,playY,10,10)
    --debug
    love.graphics.print(playY, 100, 5)
    love.graphics.print(playX, 100, 15)
end

function love.update(dt)
    if playY < 454 then 
        playY = playY + grav * dt
    end
    if playY == 456 then
        if love.keybord.isDown("right") then
            playX = playX + speed * dt
        end
    end
end

The variable playY shows the player height but it stops at different values every time.

Why is this?

Answer 1

As mentioned earlier dt is only as consistent as the games refresh rate. This value is multiplied with the velocity to give smooth gameplay.

If this is a player and you wish the y to stop at 456, you can always write

if playY > 456 then
    playY = 456
end

You can pretty much guarantee that the playY will stop at 456 every time because it will snap the player back to that spot.