From the Depths
The bare minimum is designing a hydrodynamic/aerodynamic hull, a multilayered armored chassis with multiple contingencies for varying threats, a balanced propulsion system capable of handling all sorts of terrain, efficiently packed subsystems and weaponry. This is already too hard and in-depth for most people
But a good player uses custom programmed AI to exploit everything from making their craft bob and weave to throw off enemy targetting systems, to making mass drivers propelling nuclear warheads at considerable fractions of c