Four and two stroke in the same engine. Why not?
Here we go.
No, that doesn’t tell us much. Have a gif instead.
It’s obviously an opposed piston engine. The left hand piston is the two stroke one and therefore the right hand one, whose crank rotates at twice the speed, is therefore the four stroke. It’s supposed to be much more efficient but like a lot of these unusual designs that appear it’s likely not to be heard of again.
The above is complicated, but there’s a simpler variation which uses a conventional single piston per cylinder layout and which switches between two and four stroke rather than combining them. Also supposed to be marvellous. Also likely to vanish without trace.