2D Fireworks: Real Projectile & Burst Physics

Shell Type

Launch Physics

Gravity 520

Air drag 0.985

Shell size 1.0×

Shells fired

Sparks live

How the physics works

Each shell is a real projectile: it launches with an upward speed computed from the click height so it reaches apex near the cursor, then gravity decelerates it exactly like a thrown ball. It bursts the instant its vertical velocity crosses zero — the true apex, not a timer.

launch: v_y0 = -sqrt(2·g·(y0 - yTarget))
climb:  v_y += g·dt;  y += v_y·dt
burst:  v_x = cos(θ)·s, v_y = sin(θ)·s   (θ evenly spaced + jitter)
spark:  v_y += g·dt;  v_x *= drag;  v_y *= drag

Peony — a single clean radial sphere of sparks, moderate speed and drag, no re-ignition.
Chrysanthemum — far more sparks at higher burst speed with visible glitter trails, so the sphere reads denser and larger.
Willow — fewer, heavier sparks launched slower with much higher drag, so gravity dominates almost immediately and they droop into long falling streamers instead of a sphere.
Crossette — a normal radial burst where each spark itself splits into a small secondary 4-point burst partway through its flight, doubling the physics: one explosion embedded inside another.

Click or tap the sky to launch a shell there