How to make a shadow for a triangle in CSS?

Question

Layout

How to make similar triangles with shadow?


I can not figure out the shadow for the shapes.
The triangle must be sharp.

Answer 1

Cross-browser method, that is, SVG under the hood feDropShadow plus path
Actually, we draw triangles and duplicate them, we shift two triangles along the same trajectories, we filter the first, that is, not visible triangle and assign it to the lower first triangle and get:

Answer 2

filter:drop-shadow(2px 3px 5px black);