Download of Charmstone 1.31 for Mac was available from the developer's website when we last checked. We cannot confirm if there is a free download of this app available. The actual developer of this free software for Mac is Ryan Hanson. Please check the Mac app with an antivirus before launch as it is downloaded from the developer's website, and we cannot ensure that it is safe.
From the developer:
Charmstone easily fits into your workflow with the existing macOS app switching and launching functionality, while requiring a minimal learning curve and memorization. You can use a configurable modifier key combo and move your mouse cursor to quickly launch apps or bring them into focus if they are already running. By using your spatial memory, transitioning between apps becomes seamless.