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No.110 · Backgrounds

Firefly Sync

A meadow at dusk where fireflies flash on their own clocks and nudge them toward the flashes they can see, so over half a minute scattered blinks become waves of light rolling through the grass. The pointer is a lantern: fireflies near it lose the beat and drift to its glow.

The prompt

Written for the variant you picked above: Dusk

Build a canvas 2D dusk meadow with fireflies that synchronise like real ones. Scene: sky gradient, a few stars and two noise-shaped ridges are drawn once per size into an offscreen canvas; every frame draws that, then the far fireflies, then a field of grass blades (one filled path of quadratic blades, ~1 per 3px, swaying with a sine plus noise), a lantern glow if active, then the near fireflies — so some sit behind the grass and some in front. Fireflies (~0.9 per 10,000 px², 36–130): each wanders on a slow noise field over the lower half, has a depth z (size and brightness) and a phase oscillator with its own frequency (period 1.3–1.6s). Brightness is a brief Gaussian flash around phase 0 (σ 0.32 rad) over a faint ember, drawn additively with a pre-tinted Gaussian glow sprite (stops e^(−4.4r²)(1 − r⁴), so no edges) plus a tiny bright core during the flash. Synchrony (Kuramoto): dθᵢ/dt = ωᵢ + K · Σⱼ wᵢⱼ sin(θⱼ − θᵢ) / Σⱼ wᵢⱼ over neighbours within R = max(160px, 28% of the width), with wᵢⱼ = 1 − d²/R². K ramps from 0 to 2.4 over the first 25s, so you watch scattered blinking turn into rolling waves and then a field that pulses together. Expose the order parameter r = |Σ e^{iθ}| / N via an onSync callback twice a second (the demo shows "In step · 74%"). The pointer is a lantern: a warm soft light (and a small bright core) that fades in; fireflies within ~150px (Gaussian) get jitter added to their clocks, so they fall out of step, and drift toward the light; they resynchronise after it leaves. One rAF loop, paused offscreen and in hidden tabs; ~33fps and 70% of the fireflies on touch. Reduced motion: simulate 12s up front and draw one still, synchronised frame. Selected variant — Dusk: theme="dusk": a violet sky warming to a low amber horizon, a few stars.

Notes

Interaction
Move over the meadow: your lantern scatters the rhythm nearby and draws fireflies in.
Motion
Continuous while visible; synchrony builds over ~25s; flashes ~1.5s apart.
Accessibility
The canvas is aria-hidden and decorative; overlay text sits above it. Reduced motion draws one still frame.
Responsive
Firefly count, grass and ridges are rebuilt for the new size on resize.
On touch
Touch drag carries the lantern; it fades when the finger lifts. 70% of the fireflies at ~33fps.

Featured

01Glassbreak ButtonA solid plate that fractures from one impact point, cracks racing outward as the shards drift apart.04Liquid GlassA capsule of glass that bends what's behind it, carries a specular highlight around its rim toward your pointer, and squashes like a drop of liquid when pressed.07Phosphor Glass ButtonA liquid-glass pill that senses you coming: its rim light turns to face the cursor and the pill leans in to meet it.08Iris ShutterAn async button with a camera iris for a status light — blades close and turn while it works, then open onto the result.
81Atmosphere CardSmoked-glass link cards: colour pooled in the corners, slow contour currents underneath, a field that leans toward you.93Eclipse Event CardAn editorial event plate with an oversized date and an orbital eclipse bleeding in from the right, alive with slow drift.94Specimen CardAn object mounted under glass: hover lifts the pane with a sweep of reflection and swings out a paper catalogue tag.
95Silk FieldDomain-warped light that pours like liquid silk, with an optional glass lens that refracts the flow under your cursor.106IsobarA living weather map — contour lines traced over a drifting pressure field, with your cursor as a system of its own.
151Prompt ComposerA chat composer where attached files tuck into its top edge like tabs in a folder — they rise from behind it when added and sink back when removed. Send turns into stop while the reply streams.157Aura FieldA writing field where colour only exists while the AI is touching your text: the edge becomes a turning band of light and the words are rewritten in place, one by one, out of a soft blur.
205Halftone CTAA tall CTA banner where slow gold paint drifts beneath a fixed halftone grid, visible only through the dots.
212Nocturne Sign-inA single quiet column on near-black with a breathing seam of frost light behind it — email, password, magic link, nothing more.222Sigil Sign-inA split sign-in whose left half grows a geometric mark from your email — the same address always draws the same sigil.
275Voices CarouselA testimonial exhibition: one large quote at a time on frosted glass, crossfading between voices without ever resizing.
279Feral TitleA brutal condensed wordmark — heartbeat in the dark, letters slam in, a gash tears through and the word bleeds.
301 components