I tried some sensors to make analog input and send digital output through LEDs.

At first, I tried these labs: Photoresistance+Green LED, Force-sensing Resistor+Yellow LED, and Rotary Potentiometer + RGB LEDs.

Then,  I mixed Force-sensing Resistor and Rotary Potentiometer to control the RGB LEDs. In the circuit, the Force-sensing Resistor controls the blue light’s changing from bright to dim, the two Rotary Potentiometer control the red and green lights.

The coding is as follows:

And this the video:

I cut a paper board with a heart-shaped hole to cover the LEDs. Then it maks a simple installation: if you press the button harder and harder, the red heart will become more clear.