Slain.io is a boxing sport .io game that many players are familiar boxing sport for before. You start with low boxer level and need to develop your level to attack enemies readily. If you gain enough points from enemies or non-player characters, you will level up. In addition, you can collect score points which are mixed in the map to increase your level. Your gloves and body grow depending on your level. You can see your level and experience in the middle screen. When you are bigger than another player, you can hit them strongly. Players can observe the top players kill and top levels in the top right corner of the screen. Also, there are 3 different attributes which are defensive, offensive and special. Defensive skills are max health, armor, regeneration. Offensive skills are attack damage, armor penetration, attack speed. Special skills are movement speed, life steal, damage reflection. If you sign up the game, your rank is saved and nick is special just for you. Besides, the game game shows top 20 players level and level on the login page. Therefore, many players want to level up and kill their enemies as soon as possible to have better status. The controls are very simple. To movement by WSAD or Arrow keys, to attack by left mouse button, to block by right mouse button. To sum up, defense has a significant role to eliminate your opponents in that game.