Nintaco is a work in progress. It is a NES-Famicom-Dendy emulator written in Java 8, ostensibly making it cross-platform.
If double-clicking the jar does not automatically launch the emulator, try: java -jar Nintaco.jar
Configure input: Options | Button Mapping...
If you are using an 8 button controller, such as a USB NES gamepad, try mapping Rewind Time to Start + B.
If you want to resume at arbitrary points in the past: Tools | Watch History... and Resume Here