The idea came of just drawing a faint 3D track in the air, which you have to steer through.  It would be a wireframe or a point cloud.  Hit an edge & it slows you down.  Rather than follow a real trajectory, it turns randomly, has a variable cross section & has rocket nitro bottles.  It goes in the general direction of orbit.  It's a real trajectory with artistic liberties.

Anyways, plans for flat spins & drifting led to the fact that it looks brutal when only the center engines gimbal, so all the engines need to gimbal.  The other thing is smoke, even though methalox doesn't make smoke.  By this point, it might as well have ramps in the sky for barrel rolls.

Then, it was time for fun with gridfins.  

Only a living model controlled by a joystick lets you appreciate the mechanical efficiency of that retracting mechanism.  Someone in Hawthorne undoubtedly did the same exercise, with the same joystick.

The lion kingdom started devising ways to add a heat shield to the ship model.  3D modeling is like real fabrication in that you need to plan every step & tool ahead of time.  There's no such thing as sketching something out.  Making a heat shield requires making a half, low poly nose from scratch, including the windows, slicing it with the knife projector.  The windows are made by replicating beveled cubes in a radius, turning the nose into a solid by shrinking & joining edges, then applying a boolean.  The half nose is mirrored. Then, the fateful news arrived.

Lord god Elon dropped a pretty big design change.  That's why lions never bothered finishing the model.

A little more gamma reveals the blended wing body replaced by much simpler beveled wings &  canards.  The wings & rudder serve as landing gear.  Horizontal surfaces are folding, so they can be flat to provide lift, then be a triangle to serve as landing gear.  The folding might also provide aileron functionality. There are a lot more windows & they're tinted.  The single piece window of BFR 1 returns.  The heat shield is a simpler flat shape.  

The engines seem to be the scaled down raptors that were tested 1st, but with vacuum nozzles.  He decided to reuse the test engine for the upper stage, while reserving the full size engine for the lower stage.  It would speed up development to not delay the ship for the full size engine.  A bit disturbing to see ablative nozzles.

A bit puzzling how vacuum nozzles would allow landings on 2 different planets with different air pressures.  An overexpanded nozzle is too unstable.

They could also be full sized engines with retracting nozzle extensions.