I am not sure it is a real spice at all.
Emphasis by me
SPICE-like models with a mixed-mode simulation engine
Sounds more like they use an own simulation engine.
I played a little bit with it, and I did get the expected results for my trivial circuits, no crashes. Although I didn't manage to figure out how to get a reading from the voltmeter element they offer under Unsorted Elements. But selecting a net with the cursor worked to read the voltage.
But all in all, I don't see the point in having an online simulator. I am showing my age here, new and different doesn't automatically mean better. If you look for a free-of-charge, although proprietary SPICE, then LTSpice is worth a try.