Red amber green

How is it that someone can understand logic, but not resistors?

Interesting! Thanks.

Wouldn't the diodes be acting as resistors? (Please forgive,... I'm a noob trying to learn.

Not at all. There's almost 50A (at 5V, that's 250W) going through a 2V 20mA LED. A simple 150 ohm resistor sets that straight.

You do need forward resistors. If you make this a real circuit and don't use forward resistors for your LEDs they will blow. For a 5mm led between five and nine volts use about 560 ohms and not less than 330. I should have thought to put resistors in, but in logic simulators you tend to look at LEDs as visual indicators and leave them out. Sorry.

I get your point. They're just for a visual reference. However, at proper voltages, you can see them better. The X that's displayed with then pop isn't as easy to see as the nice glow from a properly functioning LED. Plus, it just looks more professional. If I see a circuit, and the first thing I notice is the basics being passed over, or ignored, then I couldn't care less what the rest of the circuit looks like. I mean the logic if fine, and I can see the potential usefulness of the circuit, it's just that when basic things are overlooked, it sort of brings down the quality and worksmanship of the whole thing.

With then = when they. :/