Abstract: We present CrazyBeachball, a MATLAB-based graphical user interface (GUI) software package designed for focal mechanism inversion using P-wave first-motion polarity and S/P amplitude ratio data. CrazyBeachball integrates seismic waveform visualization, first-motion polarity picking, and focal mechanism inversion into a single, interactive platform. Unlike conventional methods that involve separate, independent steps, CrazyBeachball streamlines the process and eliminates the need for external data conversion. Its user-friendly interface allows for efficient focal mechanism determination, while its human-machine interaction facilitates enhanced quality control. We demonstrate its effectiveness by determining focal mechanisms for 21 aftershocks from the 2021 M_S6.4 Yangbi earthquake sequence, with results aligning with the regional stress field and fault zone geometry. This open-source software package also allows for user customization, enabling adaptation for specific research needs.