-- Lesson 2: Numbers That Change

CELL_WIDTH  = overlayGetFontWidth()
CELL_HEIGHT = overlayGetFontHeight()
TOP_ROW     = 2

word   = "Hello!"
wordX  = 0
wordY  = TOP_ROW
speedX = 0.25
speedY = 0.125
frames = 0

lastColumn = overlayGetWidth() // CELL_WIDTH - string.len(word)
lastRow    = overlayGetHeight() // CELL_HEIGHT - 1


function onOverlayUpdate()
    frames = frames + 1
    wordX = wordX + speedX
    wordY = wordY + speedY

    if wordX < 0 then
        wordX = 0
        speedX = -speedX
    end

    if wordX > lastColumn then
        wordX = lastColumn
        speedX = -speedX
    end

    if wordY < TOP_ROW then
        wordY = TOP_ROW
        speedY = -speedY
    end

    if wordY > lastRow then
        wordY = lastRow
        speedY = -speedY
    end

    overlayClear()
    overlayPrint(0, 0, "frame " .. frames)
    overlayPrint(wordX, wordY, word)
    return OVERLAY_UPDATED
end