Thanks for the feedback! We're glad you enjoyed the game :)
We hadn't really considerer click-click to merge. It would be hard to fit into the current game as you might want to click two adjacent tiles to level them up. But this is a nice suggestion to improve accessibility. We'll have to put some thought into how best to achieve this in future... Maybe an option to change the control scheme for those who struggle with dragging (or only have a trackpad!).
Thanks again!