const build_options = @import("build_options");
const EVAL_FUNCTION = if (build_options.nnue) nnue.evaluate else eval.evaluate;

    const evaluation = eval.evaluate(gs);

    const evaluation = EVAL_FUNCTION(gs);

    const nnue = b.option(bool, "nnue", "Enable NNUE") orelse false;
    const options = b.addOptions();
    options.addOption(bool, "nnue", nnue);

    // exe.linkLibCpp();
    // exe.addIncludePath("src/nnue");
    // exe.addCSourceFiles(&[_][]const u8{ "src/nnue/nnue.cpp", "src/nnue/misc.cpp" }, flags);

    if (nnue) {
        exe.linkLibCpp();
        exe.addIncludePath("src/nnue");
        exe.addCSourceFiles(&[_][]const u8{ "src/nnue/nnue.cpp", "src/nnue/misc.cpp" }, flags);
    }
    exe.addOptions("build_options", options);

    exe_tests.linkLibCpp();
    exe_tests.addIncludePath("src/nnue");
    exe_tests.addCSourceFiles(&[_][]const u8{ "src/nnue/nnue.cpp", "src/nnue/misc.cpp" }, flags);

    if (nnue) {
        exe_tests.linkLibCpp();
        exe_tests.addIncludePath("src/nnue");
        exe_tests.addCSourceFiles(&[_][]const u8{ "src/nnue/nnue.cpp", "src/nnue/misc.cpp" }, flags);
    }
    exe_tests.addOptions("build_options", options);

This engine uses a bitboard representation. A chess board got 8x8 squares, so a `u6`

This engine uses a bitboard representation. A chess board got `8x8` squares, so a `u6`

This is called the [Copy-Make](https://www.chessprogramming.org/Copy-Make) method.