It's normal. Charging state, in the charging state, the battery will generate heat, which is a normal phenomenon.
Playing large mobile games or applications will take up a lot of CPU resources.
When using the mobile phone while charging, it is recommended to use it after fully charging.
The use of mobile phones in a closed environment, because the mobile phone is in a closed state, the heat does not go out, will lead to serious fever, it is recommended to use in a well-ventilated environment.
Use mobile phones for long periods of time, such as long conversations, playing games, etc.