T - Touched : I have used this software/tool at least once either while exploring options for a project or due to my curiosity from someone mentioning it.

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D - Developed: While working on a project I used the software/tool on multiple occasions and while doing so have read parts of the documentation and read/watched/contributed to the Stack Overflow/Reddit/YouTube/etc... conversation concerning said software/tool.

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C - Contributed: I have merged my contributions into a version controlled open source/proprietary project.