Yes, same here (Spain), but the rate is also higher than what the OP said for Brazil (ranges from 20% to 25% here).
If the OP is a gambler, I'm sorry to hear that from now on he will have to pay if he is successful if he was used to don't care about it. Financial management of gamblers is always hard, and having to add this new requirement to the equation complicates things even more.
Sorry to say but it seems like Brazil can now only survive on the money the government makes from casino taxes it seems.
15% from gamblers and 12% from casinos, isn't that looking like corruption on its own? Because this amount is alarming as if it's the only way the country can grow, this is a lot of money, imagine if Brazil has a million gamblers as a minimum.
If I am living in Brazil I will have to stop gambling because it's the most targeted for the Brazilian government right now, and if this tax is shifted to other things like businesses then it's a calling to leave the country behind.
Hearing that yours @porfirii is even up to 25% is disheartening, in my country gamblers don't pay any taxes but the casinos do pay heavily on tax settlement, which I believe is the way it should be, casinos are always making money, and they can afford it.