This is LED flashing circuit, the circuit is quite simple. Alternatively, you could be create another shape, not just heart shape.
|R1, R2||–||470 ohm, 1/2-watt|
|R3-R5||–||100 ohm, 3-watt|
|R6-R8||–||1000 ohm, 1.4-watt|
|R9||–||5000 ohm potentiometer|
|C1, C2||–||100uF, 16 volts, electrolytic radial|
|IC1||–||4047, low power monostable/astable multivibrator|
|Q1-Q3||–||2n3643 NPN transistor or equivalent|
|LED1-LED84||–||yellow light-emitting diode|
|LED85-LED126||–||red light-emitting diode|
|LED127-LED142||–||green light-emitting diode|
|PS1||–||12VDC @ 500mA wall transformer|
|Miscellaneous: Jumper wire, solder, printed circuit board,|
|drill and bits,14 pin I.C. socket, and a frame or case.|
Once power has been applied to the circuit, the Red LEDs should all be flashing on and off together. The Yellow LEDs should be flashing on and off, but only every other Yellow LED should be on at one time. The Green LEDs will stay on at all times. The flash rate can be adjusted by turning R9. Connections for a fixed value resistor for R9 are provided on the board layout if preferred.To dress up the project, a favorite photograph can be placed in the heart, and a frame can be made to fit the circuit board.
Complete explanation, please visit this page