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 - How to find and use [Datasheets](https://datasheet.octopart.com/ATTINY45-20SU-Atmel-datasheet-41301906.pdf).
 
 - For example, look up part in [Digikey](https://www.digikey.com/) or find in [Octopart](https://octopart.com/).
+
+- Simple Simulation tools.
+  - [Tinkercad](https://www.tinkercad.com/)
+  - [Falstad Applet](https://www.falstad.com/circuit/)
 ___
 
 ###Outline.