It’s time to make hearts with their very own LED and battery for the light of your life. 
 
Here’s what you need to buy:
  • Cardstock
  • 1/4″ Copper Tape 
  • CR 2032 Coin Cell Batteries
  • 5MM LED Bulbs
  • Paper or Binder Clips
Directions:

Step 1: Bend the leads on the LED at a 90-degree angle so that they can lay flat on the cardstock. If the leads are too long to follow the heart line, you can cut them shorter, but make sure to keep the positive lead longer for easier building.

Step 2: Try to use long continuous sections of copper tape without breaks. If it does break, give about an inch of tape overlap with the next section.

Step3: Tape the positive LED lead with copper tape so that it secures the lead to the card and travels down the right side of the heart, all the way to the switch tab battery section.

Step 4: Repeat with the negative LED lead and tape down the left side of the heart to the positive battery circle.

Step 5: Place battery with the positive side up and close the card. Secure the switch with your finger/paper/binder clip.

References: https://leftbraincraftbrain.com/light-circuit-valentines/