C4 really has some good ideas by its own.
* It never bothers to produce a machine code. The use of stack-based VM simplifies the single-pass compilation, and it never makes use of unknown library functions so no machine-specific knowledge is required (like dlsym in Bellard's OTCC [1]).
* It chose its primitives wisely. It never implements structs and returning with values, for example, but the code is carefully structured that the lack of them doesn't make it harder to read.
* And yet it has tons of little tricks. Switching from r-value to l-value (triggered when infix `=` or postfix `++`/`--` are read) is a single opcode fix. Reserved words are initialized from an imaginary source code. The type is represented by a single number 2n+k where n is the number of indirections.