not a bug, it's actually real transistor behavior 🙏🏽 your LED sits after the last transistor's output (emitter), so when B is on, B's base current flows through the base, out the emitter and straight into your LED, even with A off. that's also your 12 vs 14 mA: emitter current = collector current + base current, so B's ~2 mA joins in. a real breadboard does the same thing. fix: put the LED before the transistors (+ → resistor → LED → transistor → transistor → ground), each input through a resistor into a base. I built both in game: yours lights on 0/1, the fixed one is a perfect AND. for bug reports please use the discord (/bug), it's on the game page and in the download instructions, so I can actually track them: discord.gg/tinylogic