After the Oracle Bones script, there was a long period where the script changed slowly and not totally uniformly across China. These scripts are sort of all called “Large Seal” or “Great Seal” or “Bronze Script”.
Eventually, in around 220BC, a gentleman named Li Si 李斯, acting under the direction of Emperor Qin Shi Huang, regularized the script. That script is called “Small Seal Script”, “Lesser Seal Script”, or sometimes just “Seal Script”, and was made the official written language of the empire. This was probably not the first time and was certainly not the last time that a government mandated the orthography of a writing system.
This script is still in use today, although its use is limited. It is the script most commonly used on stamps used to verify identity called “chops” and where the writer wants to invoke feelings of tradition. I see it most often in signs for Chinese restaurants or antique shops. It has a more rounded look to it than more modern Chinese scripts, and generally uses constant-width lines instead of lines that look like brush strokes.