Hikizan

The game lasts for three minutes, and players compete to see who can get the most correct answers within the time limit. The game involves subtraction (can also be set to addition), and you just keep subtracting 17 (the number can be changed). There is a simple strategy for this game; first subtract 20 and then add 3. The buttons are arranged so that 6 is below 3 and 9 is below 6, so you can get the answer without doing any calculations, but... Humans can't concentrate for three minutes. Your thinking speed gradually slows down, you start to panic, and then you recover a little and the game ends... It's always like that. It's a game that seems simple but is difficult. I heard this later from an acquaintance, but there is apparently a brain training method to prevent dementia, where you subtract 7 from 100. Coincidences are scary. It's simple calculation by hand. You have 180 seconds to solve the puzzle, so if you solve one puzzle every three seconds, you can solve 60 puzzles. But in reality... This is a game that will help you develop your judgement and concentration. It's a fun game that can be useful in real life. Try it out to train your brain and kill time.