View.Set ("graphics:max,max")
var size : int := 50
var mx, my, mb : int
var ballx, bally : int := 200
var dirx, diry : int := 0
var ballSpeed : int := 1

dirx := ballSpeed
diry := ballSpeed
loop
    mousewhere (mx, my, mb)
    drawfillbox (mx - size, 0, mx + size, 50, black)
    drawfillbox (mx - size - 1, 0, 0, 50, white)
    drawfillbox (maxx, 0, mx + size + 1, 50, white)
    drawfilloval (ballx, bally, 15, 15, white)
    ballx += dirx
    bally += diry
    drawfilloval (ballx, bally, 15, 15, blue)
    if ballx >= maxx then  % right wall
        dirx := - (dirx)
    elsif bally >= maxy then % top wall
        diry := - (diry)
    elsif ballx <= 0 then  % bottom
        dirx := - (dirx)
    elsif bally <= 0 then  % left wall
        diry := - (diry)
        locate (1, 1)
        put "lost ball"
        ballx := 200
        bally := 200
        loop
            mousewhere (mx, my, mb)
            exit when mb = 1
        end loop
    end if
end loop