The BeatScript (BS for short) is a command-based domain-specific scripting language.
...Though it really is just a kind of (virtual) Assembly language, with a custom set of instructions.
BeatScript is interpreted line by line, and tokens are separated by spaces or periods (,). They can be mixed, but it is not recommended.
Every line begins with the name of the instruction, followed by a sequence of parameters associated with it.
{INSTRUCTION} {PARAMETERS...}
Comments are also supported. Lines that begin with // (C-style) or # (Perl, Python) are treated as comments and are ignored by the interpreter. Empty lines are also ignored.
Yep. That's it. Simple, isn't it?
Right now, aside from the typical syntax rules, the only extra rule is that every script file should at least specify BPM once with the BPM instruction. It doesn't have to be at the top of the file, but it is recommended that it is put there.
In SongManager.cs, look for the LoadBeatmapScript public method.
You can insert new instructions by adding new case statements.
A rule of thumb is that you should assert the number of tokens in the line before you do anything with the parameters, and log the lineCount variable if an error occurs. In the picture above, the BPM instruction expects one parameter, so a line with BPM as its first token should have two tokens in total. That's why we assert that tokens.Length == 2.
Instructions can be associated with a timestamp (like the AIRNOTE instruction), or they can be configuration commands (like the BPM instruction).