Volts and amps, the latency budget, the servo angle — short honest explainers with the numbers you'll actually use on a build.
Every LED question is a battery question. Single-color strips sip current (~0.4 A/m), analog RGB sips more when white, and addressable Neopixels at full white gobble ~60 mA per LED — a 3-meter 60-pixel strip can want 3+ amps at full white. The cheat: never plan on full white. A dimmed preset at 40% reads just as bright on a con floor and doubles your battery life. The wiring rule: inject power every 2 meters of strip, and keep data wire short.
An effect "reads" when it lands within ~100 ms of the gesture — quicker than a blink. Playing from the watch's own speaker: gesture to sound is essentially instant. Route through a Bluetooth speaker and you add 150–300 ms; the cue arrives as drama instead of impact — for whooshes and ambience that's fine, for a sword clash it reads as lag. Full table on the why sound reads note.
A hobby servo takes a pulse train and holds an angle between ~0° and 180°; the width of the pulse (1–2 ms) IS the instruction. For a puppet eye-blink or brow mech, mount the horn to the mechanism with push-rod linkages and drive it from any RC tester or board — the app's gesture zones can even cue a compatible prop. Torque matters: heavy heads want bigger servos, and every servo wants its own clean power.
Bare LEDs read as points; costumes read as glow. Put 8–10 mm of diffusion (_ping-pong halves, translucent silicone, frosted acrylic_) between the LED and the eye and the point becomes a soft source. Double-diffuse for faces and visors: one layer of silicone over one layer of frost-acrylic kills the hotspot without dimming the color.
Linear fade vs gamma-corrected fade: same loop, different read. The curve is why cheap dimmers look cheap.
Pulse width to angle, then angle to linkage — watch the horn move and the push-rod follow; that's a blink in the making.
Sixty seconds, six questions, one honest recommendation.
Nine crafts, free build sheets, workshop video, and the app that fires the cues. Start anywhere.