1. Add parts from the left rail. They stack bottom→top: engine → tanks → pod → nose. Click any part in the 3D view to remove it.

2. Watch TWR (must be ≥ 1.0 to leave the pad) and Δv (must beat the mission budget).

3. Add a DECOUPLER to split into stages — drop the dead weight, fly further. Build engine + tanks above each decoupler.

4. Pick a mission and hit LAUNCH. A bad rocket failing is the lesson — iterate.

Δv = Isp · g₀ · ln(m_wet / m_dry)  ·  TWR = thrust / (mass · g₀)