Drawing Heart Optical Illusion with Pencil - Convex or Concave Heart?

Drawing heart optical illusion with graphite pencil. Is it Convex or Concave Heart? Drawing heart in line paper. Trick art on line paper with Vamos.
Paper: 250x175 mm, white coloured cardboard.
Graphite pencils (STABILO HB) and DERWENT 8B.
STABILO Pen marker.
Kneaded eraser, ruler.
Cotton material.
♪ MUSIC:
Rauchus by Twin Musicom is licensed under a Creative Commons Attribution license
(https://creativecommons.org/licenses/...)
Artist: http://www.twinmusicom.org/ /
By Sandor Vamos. I'm Hungarian.
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