Just dont click done before you have to, easy as that.
no, its not as easy as that, when your hand twitches, or something and you mistakenly hit the space bar. thats one of my problems, i get comfortable, then while im using my turn, my thumb, or a finger will twitch, making me hit the space bar. "keep your hand away from the space bar till your ready then" ya, i try... but it ends up back in that spot. its a habit to keep my hand there. yes, i agree, a confirmation for turn end would be annoying. but it would save people from making those small mistakes that may or may not cost them the match.
your opponent has 18 health left, you have your dragon, an abomination, and a weapon. in total doing 17 damage. your able to summon a creature that will do 1 damage. and win the match. but oops, you accidentally hit the space bar, ending your turn. you had 2 points left. and your opponent wins. you lose gold, and score points. and who knows. that loss could have been avoided if you would have had a confirmation asking if you want to end your turn. but because you didnt, your pissed, cursing the game. because you could have won if it didnt just instantly end your turn.. and you will be wishing there was a confirmation that would have saved you from the loss