the photo in burden.ppm is "selective focus photography snowflakes" by aaron
burden. it can be found online at
https://unsplash.com/photos/selective-focus-photography-snowflakes-9yhy1FXlKwI.
its license can be found online at https://unsplash.com/license.

the icon in pointer.ppm is released under the cc0 1.0 universal public
domain dedication (https://creativecommons.org/publicdomain/zero/1.0/).
