DONE: rework type system
DONE: var decl with a type, but no value
DONE: type casting

TODO: string concat with the + operator
TODO: empty string as falsy?
TODO: remove optimization option
TODO: increment & decrement operators
TODO: a = b = c = 1;
TODO: are compounds shallow or deep copies?
TODO: conditionals
TODO: if-then-else
TODO: chained if-then-else
TODO: optional block around a path if it's only one statement
TODO: while-then
TODO: for-then
TODO: break and continue statements
TODO: functions, and all of their features
TODO: Assertion-based test scripts
TODO: standard library
TODO: external runner library