Test Key Event

local x, y = 1, 1

local xSize, ySize = term.getSize()

while true do
    -- Draw a white space at the current x/y co-ord:
    term.setBackgroundColor(colours.black)
    term.clear()
    term.setCursorPos(x, y)
    term.setBackgroundColor(colours.white)
    term.write(" ")

    -- Wait for a key event:
    local event, key = os.pullEvent("key")

    -- Act on it:
    if key == keys.up and y > 1 then
        y = y - 1
    elseif key == keys.down and y < ySize then
        y = y + 1
    elseif key == keys.left and x > 1 then
        x = x - 1
    elseif key == keys.right and x < xSize then
        x = x + 1
    elseif key == keys.q then
        break
    end
end