Special NAND gate
Still remember what the NAND gate is? Its output is 0 only when all inputs are at 1, and 1 when the inputs have any other combination-reverse of the AND gate. Let's find out how this circuit works, using a NAND gate IC.
Note that inputs are 1 when keys are pressed, and 0 when released.
When you finish assembling the project, press/release S1 and S2 while watching Figure 1 and see how the LED blinks ON and OFF.