Concept
The main concept is to create a switch that isn’t necessarily a physical switch but a gate that returns true when a requirement is fulfilled. I created a switch that can provide an alert based on the water level of a specific environment. The circuit looks like this:
The two switches at the bottom part of the board indicate the water levels. Whatever the water level is, the rightmost LED always shines. If the water level is above a threshold, the second LED shines too. If another threshold is met, the third LED shines. This serves as an alert system for the water level of a specific environment. The actual functional circuit is shown below:
This is what happens when there is no water in the cup.
This is what happens when the water in the cup only reaches the first threshold
This is what happens when the water level reaches the maximum value.
This is what happens when I disconnect the second LED, because the power the red LED needs is more than the yellow one needs, so it might not be obvious that the red one is shining. This image is to show that the red one is shining when the water level is high.