How designed circuit works?

When the battery is turned on, the high-frequency oscillator composed of the transistor Q2 and the step-up transformer T1 is energized using the 3V DC supply generating a high-frequency alternating current of about 18kHz, boosted by T1 to about 500V. This high voltage ranging at 500V is then further stepped up using a ladder network, which is made up of three 1N4007 Diodes, capacitors C2- C4. This network steps the T output to approximately three times its original value and we get around 1500V which gets stored inside a high voltage PPC capacitor positioned at the extreme end of the ladder network. Now for bug counter purpose, I am sensing the voltage on the output cap, I added a few diodes D1-D3 on the bottom side so that you see a high to low transition when a bug is zapped. This works only if the output cap is fully discharged when a bug is zapped, which is unlikely. Worth a try if you have some diodes around, and a fair amount of bugs too. Further, Arduino nano is used to count these output from the diode, and display on an LCD.