The default canvas (Arduino Uno + LED on pin 13) wired the LED
directly between pin 13 and GND. Two consequences:
1. Real-world: that's a short across a forward-biased diode,
blowing the LED in seconds.
2. Simulator: ngspice can't find a steady-state branch current
for an unprotected diode (returns NaN / indeterminate), so
the LED visual never lights up. Only the wokwi-arduino-uno
element's BUILT-IN LED (rendered internally by the element,
not via wire+pinManager) was visible.
Fix: insert a 220Ω resistor between pin 13 and the LED anode,
cathode straight to GND. Same circuit every introductory Arduino
book teaches. SPICE converges, LED blinks visually on the canvas.
Reported by a user trying Blink on a fresh /editor visit.
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