Ferrari - one of a number of options
The combustion engine is, in the primary embodiment, an inline-six fueled by hydrogen gas. It's an inline engine because that configuration provides room for hydrogen tanks on either side of it. The engine is also mounted upside down, i.e., the crankshaft is at the highest point of the engine while the cylinder head sits directly above the road.
The logic behind this is that the transaxle can now be placed higher up on the engine, which means a more aggressive diffuser can be installed at the back of the car. Some World War II fighter aircraft had upside-down engines like this, so it's not completely unheard of.
The same aggressive diffuser would be possible without this unusual arrangement, but the vehicle would be much longer—and the document insists a short wheelbase is very important.
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