Assemble this circuit on brick adapters:
power + wire + light sensor (light mode)+ wire + DC motor + buzzer
Build a heart
Build a lego heart as shown in the pictures, or substitute your own paper/cardboard heart.
Build a tower with shelves
Build a lego tower with 2x6 bricks or a combination of 2x4 and 2x2 bricks. Make shelves with 4x6 base plates. This is where your brick adapters will rest. I made 3 shelves:
1) The bottom shelf holds an upside down brick adapter underneath it for the power + wire.
2) The middle shelf holds an additional 4x6 base plate at a 90 degree angle. This is where I situated the wire + light sensor + wire on a brick adapter.
3) The motor sits on the top/center of the tower on a brick adapter with a buzzer next to it.
Test & adjust
Rearrange the shelves and adjust the light sensitivity so that the heart can cast a shadow on the light sensor only some of the time. That way the motor will go slower sometimes, and the buzzer will go on and off. It takes patience to make this electronic valentine turn on when someone turns on the light, but it is possible.