A learner playing the puzzle game Electronics Puzzle Lab ran into a confusion that trips up almost everyone the first time they meet digital logic: a NOT gate with nothing connected to its input still produces a HIGH output. To the beginner, this looks like a signal materializing from thin air — a violation of conservation. The 41-comment thread that follows is a lovely crash course in the gap between the abstract logic-gate symbol and the real silicon underneath.

The key insight from the responses: in digital electronics there is no such thing as "no signal." A wire is always at some voltage. What the game calls "no input" is actually the input being pulled to logic LOW (0 V, ground), and inverting LOW gives HIGH. In real CMOS or TTL parts, a truly floating input isn't "nothing" either — it's an undefined, high-impedance state that will pick up noise, oscillate, draw shoot-through current, and generally misbehave. That's why every datasheet insists on pull-up or pull-down resistors on unused inputs.

Several commenters take the explanation deeper, which is what makes the thread educational:

• Power is the source of the "new" signal. A NOT gate isn't conjuring energy; it's a tiny switch (a pair of complementary MOSFETs, in CMOS) that connects the output either to Vcc or to GND. The output's HIGH comes from the supply rail, not from the input.
• Logic levels are voltage ranges, not points. TTL treats anything below ~0.8 V as LOW and above ~2 V as HIGH, with a forbidden middle band. The game's binary abstraction hides this entirely.
• Floating inputs are dangerous. On a real 74HC04, leaving an input unconnected can cause the gate to hover in its linear region, dissipating power and producing garbage output. Pull resistors define the default state.
• The symbol lies a little. Schematic NOT gates omit the Vcc and GND pins for clarity, which is exactly what causes the "where did the energy come from?" confusion.

The thread is a great example of why beginners should bridge gate-level simulators with real breadboard work early — the simulator's clean abstraction is helpful for learning Boolean logic, but it actively misleads about how physical gates behave. Anyone moving from games like NAND-game, Turing Complete, or Electronics Puzzle Lab toward actual hardware should read this before they wire up their first 7404.