1. No GND loop to the MCU
2. 2k7 ohm R at the gate of 2n3904 is too big. LED not as bright. 2n3904 has 200mA capacity for collector-emitter. I’d like to saturated it. Assuming a current gain of 15, 13mA is all I need at the base. (3v3 – 0.65v) / 13mA is 203ohm.
3. Without a proper push button, electrical noise generates false input, resulting in random LED toggle
4. Should have labelled the PCB better. Hard to figure out which pin is what
5. Need to extend support for multiple LED