The default layer is colemak with backspace instead of ; It can be switched to qwerty on the firmware layer.
All layers use Tap Toggle to lock them temporarily after pressing it 3 times. Reset to default layer by pressing the same button once more. Arrow layer can be accessed by both hands. This makes deleting letters and tabulating possible with one hand on the mouse.
Symbol layer is designed to have the most used symbols in programming in the most accesible places.
Brackets and = sign are the same as in the symbol layer. Dollar and Percent are swapped because i barely use dollar sign. The most used symbols paired with numbers are there. It can be accesed comfortably by left hand thumb and also optionally by pressing both right-hand thumb keys to allow one handed usage from time to time.
System layer - this is where all function keys and pc related shortcuts are placed.
Mouse layer is kind of symetrical for both hands.