How does the snail's shell grow with it?

To be exact, it is not "growing up", but a new shell grows outside on the original basis.

Snails like to live in a dark, humid, loose and humus-rich environment, lying during the day and coming out at night. They are most afraid of direct sunlight and sensitive to environmental reactions. Their most suitable environment: temperature16 ~ 30℃ (the fastest growth is at 23 ~ 30℃); Air humidity 60% ~ 90%; The humidity of the feeding soil is about 40%; The pH value is 5 ~ 7. When the temperature is lower than 15℃, it will hibernate when it is higher than 33℃, and it may freeze or heat to death when it is lower than 5℃ or higher than 40℃. But all kinds of snails are different.