Shoot, thanks for reporting this! And it's very kind of you to offer to support the project — thank you so much.
We have noticed that it does not work very well on older Macs or on Macbook Airs — We have tested it on newer Macbook Pros and it seems to work well on those. We think it's because the processing power on the older Macs aren't able to handle the software, unfortunately.
If we can't fix it, we will update our minimum requirements as soon as we have a better picture — And hopefully you'll be able to reinstall and use it on another device in the future, but I'm so sorry for the inconvenience.