Design notes

Decisions that aren't obvious from the code, and the measurements behind them. Written down because each one looks wrong at first glance, and each was arrived at by getting it wrong first.

• Final newlines — why server text and local files convert unconditionally in both directions, why puzzles and contributions differ, and how CodinGame's output comparison actually behaves.
• What CodinGame actually runs — measured compiler, interpreter and library versions, and the -O0 finding their docs don't mention.
• Composable toolchain images — why one image carries every language, and how fragments compose so a subset shares layers with a superset.
• The documentation toolchain — why the site is built with ProperDocs rather than MkDocs, why MkDocs 2.0 is not a destination, and the page-count test that decides when Zensical becomes one.

What belongs here

Anything a future reader would otherwise re-derive, re-argue, or "fix" back to the broken version. Not a substitute for docstrings: if it explains one function, it belongs on that function. These pages are for decisions that span modules, or that rest on evidence living outside the codebase.

Where a claim was established by probing the live service, these pages say when and how, so it can be re-checked rather than trusted indefinitely. CodinGame is free to change any of it without notice.