In fact, shell units are three-dimensional and planar, that is, each unit has its own shape. Look at the English description of Unit 63. There is a circle number in the explanation of the unit, which is the direction of the unit. You need to use the sfe command to increase the downward pressure.
The emergence of mathematical symbols:
Counting symbols on wood, bones or stones have been used since prehistoric times. Stone age cultures, including ancient Indians, used counting symbols in gambling, private services and transactions.
From 8000 BC to 3500 BC, Sumerians invented the use of clay to retain digital information. Their practice is to string together small mud marks of various shapes like beads.
Clay symbols are gradually replaced by numerical symbols. These digital symbols are carved on the clay block with a round pen needle and then fired. About 3 100 years ago, digital symbols were separated from counted things and became abstract symbols.