Try Drone Lab free in your browser, with nothing to install and no account. Design a drone from real parts and see if it flies. Pick a frame, motors, props, a flight controller and a battery, each with the specs a hobby shop lists, and put them together on the bench. Test one motor and prop on a thrust stand, check that each motor spins the right way with the props off, then hover it. The numbers decide what happens: too heavy and it will not lift, a prop on backward and it flips, the battery too far back and it drifts. Customers ask for a drone under 250 grams, one that hovers 14 minutes, or one that carries a package.