bounce

-------------------------------
-- logMcTime() and logIndent()
-------------------------------

local function logMcTime ( logLine )
    nTime = os.time()
    mcTime = textutils.formatTime( nTime, true )
    write (string.format ( "%-6s => %s", mcTime, logLine).."\n" )
end

local function logIndent ( logLine )
    write ( "         "..logLine.."\n" )
end

-- global defines
local monTab = { }
local cursorSize = 3
local directions =  { "top", "bottom", "left", "right", "front", "back" }

-------------------
-- monDump()
-------------------

local function monDump ( dumpMon )
    local logLine="Monitor on "..dumpMon.SideUp.." is"

    if dumpMon.Connected == false then
        logLine = logLine.." not connected!"
    else
        logLine = logLine.." connected!"
    end

    logMcTime( logLine )

    if dumpMon.Connected == true then
--        logMcTime( logLine )

        logLine = string.format( "WxH: %d x %d ITEMS: %d ", dumpMon.Width, dumpMon.Height, dumpMon.ItemCount).." "
--        logIndent( logLine )
        logIndent( logLine )
    end
end

-------------------
-- itemInit()
-------------------

local function itemInit ( monRef )
    local newItem = {}
    newItem.x = math.random ( monRef.Width - 3 )
    newItem.y = math.random ( monRef.Height - 3 )
    newItem.dx = 1
    newItem.dy = 1
    if math.random ( 0, 1) == 1 then
        newItem.dx = newItem.dx * -1
    end
    if math.random ( 0, 1 ) == 1 then
        newItem.dy = newItem.dy * -1
    end

    return newItem
end

-------------------
-- monInit()
-------------------

local function monInit ( Side )
    local newMon = { }
    newMon.Side = Side
    newMon.SideUp = string.upper ( Side )
    newMon.Connected = true

    -- check if monitor is connected
    if peripheral.getType( newMon.Side ) ~= "monitor" then
        newMon.Connected = false
        monDump( newMon )
        return newMon
    end

    newMon.Handle = {}
    newMon.Handle = peripheral.wrap( Side )
    newMon.Handle.clear ( )
    newMon.Handle.setCursorBlink( false )
    newMon.Width, newMon.Height = newMon.Handle.getSize()
    newMon.Items = {}

    newMon.ItemCount = math.random(5)+2
    for i=1,newMon.ItemCount do
      newMon.Items[i]=itemInit( newMon )
    end

    monDump(newMon)
    return newMon
end

-------------------
-- itemUpdate ()
-------------------
local function itemUpdate( Item, scrWidth, scrHeight )
    Item.x = Item.x + Item.dx
    Item.y = Item.y + Item.dy

    if Item.x <= 1 or Item.x >= scrWidth - cursorSize then
        Item.dx = Item.dx * -1
    end

    if Item.y <= 1 or Item.y >= scrHeight - cursorSize then
        Item.dy = Item.dy * -1
    end

    return Item
end

-------------------
-- cursorDraw ()
-------------------

local function cursorDraw( monHandle, x, y, bReset )
    local cursor = {}

    if bReset == true then
        cursor = {"   ", "   ", "   "}
    else
        cursor = {"X X", " X ", "X X"}
    end

    for i=1, 3 do
        monHandle.setCursorPos( x, y+i )
        monHandle.write(cursor[i])
    end
end

-------------------
-- monUpdate()
-------------------
local function monUpdate(monRef)
    if not monRef.Connected then
        return monRef
    end

    for i=1,#monRef.Items do
        local Item = monRef.Items[i]
        cursorDraw( monRef.Handle, Item.x, Item.y, true )
        monRef.Items[i] = itemUpdate ( Item, monRef.Width, monRef.Height)
        cursorDraw( monRef.Handle, Item.x, Item.y, false )
    end

    return monRef
end

-------------------
-- gameLoop()
-------------------

local function gameLoop ( monTab )
    local gameEnding = false

    while gameEnding == false do
        for i=1,#monTab do
            monTab[i]=monUpdate(monTab[i])
        end
        sleep(0.03)
    end
end

-------------------
-- main()
-------------------

term.clear()
term.setCursorPos( 1, 1 )

for i=1,#directions do
    monTab[i] = monInit(directions[i])
end

gameLoop ( monTab )