Also, in practice, there's no such thing as a truly sharp corner, which makes sense intuitively based on the math, I think. But real systems have inertia, frict

Also, in practice, there's no such thing as a truly sharp corner, which makes sense intuitively based on the math, I think. But real systems have inertia, friction, stray resistance/capacitance/inductance, etc. so you can't have a truly perfect square wave in a physical or electrical system in the real world.