In this flashing led lights circuit, the LDR or photoresistor is connected in such way that when the light intensity varies it will influence the flashing frequency and the brightness of the LEDs. T1, T2 = BC547, BC548, BC549 (any NPN transistor).
You can arrange the LEDs D1 to D4 in cross in order to obtain interesting effecs. The whole flashing led circuit is powered from a 9 volt battery and can be built small enough so it will fit in a matchbox.
Schematic of Flashing Lights with photoresistor
