This document discusses the advantages and challenges of ethnomathematics and introduces culturally situated design tools (CSDTs). The key advantages of ethnomathematics include defeating myths of genetic and cultural determinism, using math to bridge cultural gaps, and contributions to mathematics. Challenges include issues of authenticity, ownership, and ensuring CSDTs do not ghettoize students but instead spread knowledge. The document then describes several CSDT projects including on African fractals, a synthesizer tool for polynomials, and designs from Navajo students. It concludes by discussing plans for programmable CSDTs and a CSDT community site.