[Matthias247]

Besides whats called out by others: It would be nice to have the usual action of "press both mouse buttons" on a number to open all non flagged fields around it. That reduces the amount of required clicks a bit.

But maybe its intentional to avoid one player scoring too many points at once?

[Arnavion]

That does work already. You don't even have to use both mouse buttons, just left click is enough.