You can play 1v1.lol in a99.io as unblocked.
1v1.LOL is an action online game where you can shoot and install platforms. The game is similar in theme to Fortnite. The game offers you multiple modes so you can play the battle royale or a quick 1v1 action won by the last man standing. There, you will try to form your defense and kill your opponent. There will be 3 weapons and many platforms available. You can play with a friend, but you need to register. Building the platforms can be a little tricky at first, but you will definitely get used to it.