Major library changes:

On 2021-01-01 we started using a gifted digital caliper, every single bricks will have to
   be remeasured! While we are at it, more details may be added
On 2022-01-01 we started adding sprue()
On 2022-01-01 we started changing minifig their heights
On 2022-02-20 we started flattening llogo()
On 2022-07-23 we started adding a 0.2 bevel to tiles
On 2022-07-23 we started using new basic_round_button
On 2022-08-07 we started using inset open buttons for inverted slopes
On 2022-12-04 started changing the upper wall thickness to 1
On 2023-03-20 we started using a proper 50mm camera angle definition,
   because the Fedora Linux version required a defined camera angle
On 2023-04-16 flat height went from 3.1 to 3.18
On 2023-04-23 all clips and bars went to y=2.45
On 2023-04-23 Changed button cutter sizes
On 2023-05-12 tile height went from 3.18 to 3.15
On 2024-06-19 we started rerendering all reference bricks with new reference colors
On 2024-11-30 we started using rounded_opening_for_plates
On 2025-06-09 the anti_stud() macro was introduced, with a changed diameter
On 2025-07-23 the more realistic axle_section() was introduced, with
   appropriate axle_endings
On 2025-08-09 the main reflection value was changed from 0.025 to 0.0525, a stronger
   reflection, causing much appreciated additional contrast in images as well!

As of here reference images need to be redone, bricks after this date can be considered
to be final.

On 2026-01-26 we started adding printed bricks to ultra_material.lib,
   minifig_head_with_standard_grin_pattern(color_tex,age)
