Step 4: Feeling Loopy

Awesome. We should be ready to go, right? Wrong!

There's one thing missing. You see, the most you'll ever be able to move the dot is by one pixel. That's because our code is only run once. If you really want to see it move, you need a loop, or code that will run over and over again. Spin has the repeat command for this.

repeat
    foo(bar)

To put your code inside a repeat, just put it after and indent it, and it'll loop forever! Don't just put the controls though. You need the drawing code too, like this.

Snake.spin

    snakex := 32
    snakey := 32

    repeat
        ctrl.Update

        if ctrl.Left
            snakex--
        if ctrl.Right
            snakex++
        if ctrl.Up
            snakey--
        if ctrl.Down
            snakey++

        gfx.Sprite(@dot_gfx, snakex, snakey, 0)
        lcd.Draw

You'll notice right away something really wonky. The snake is leaving a giant trail of snake behind it, to the point that this seems more like a paint program.

gfx.Clear to the rescue! This command clears the screen to black, and should be called any time you need to reset the screen. Usually the best place for it is the beginning of the loop.

Snake.spin

    snakex := 32
    snakey := 32

    repeat
        gfx.Clear
        ctrl.Update

        if ctrl.Left
            snakex--