Right click for everything in the game, from killing enemies to interacting with shops to picking up potions and scrolls
But you can only leftclick to buy items in shops.
Doesn't work well, doesn't flow. Confusing for no real reason.
Suggest left click be used for all "soft" targeting, including highlighting items to see more detail, soft targeting enemies, soft targeting shops to allow use of abilities withouth moving to or auto-attacking.
Right click for all interaction, including buying items,