Each visitor who lands on the campaign page pledges with probability
p = base + s·BW·f²/(f²+h²)·(1+urg·(t/T)³)
where f is the visible funded fraction (raised/goal), s is the bandwagon-strength slider, and the last factor sharpens the pull as the deadline nears. A small base rate keeps the campaign moving even at $0 raised; the rest is social proof compounding on itself — a positive feedback loop that produces the classic J/S-shaped funding curve. Tap the canvas to inject a burst of visitors.