crystal-robots

A great way to learn about programming with a simple Ruby-like syntax. Write programs to battle it out with other programs on a virtual battlefield. Then, learn about how programming languages turn your code into instructions a machine can understand.

crystal-robots is inspired and derived from:

• CROBOTS - a programming game, for programmers, or aspiring programmers,
• the Crystal Programming Language - A language for humans and computers,
• and chasm - a simple compile-to-WASM language.

crystal-robots is my exploration of depending on my own programming tools, taking control over a programming language itself.

• Play, read the manual, and try a challenge
• Source on GitHub

Following along

The project’s story is told commit by commit on the main branch and in the project blog.

Installation

shards build            # produces bin/crystal-robots
bin/crystal-robots -h

Crystal 1.14 or newer. Running the emitted WebAssembly (the specs and, later, battles) needs the wasmer runtime; see Development below.

Usage

bin/crystal-robots is one binary with several faces:

bin/crystal-robots -t examples/counter.cr           # print the parser derivation, one line per pass
bin/crystal-robots -i -l 5000 examples/counter.cr   # run robots in the interpreter, 5000 steps each
bin/crystal-robots -m 3 -l 100000 --seed 7 examples/counter.cr examples/rabbit.cr   # three seeded matches
bin/crystal-robots -c examples/sniper.cr -o sniper.wasm # compile a robot to WebAssembly (imports env.scan, env.cannon, ...)
bin/crystal-robots -c examples/sniper.cr --ticks -o sniper.wasm # also import env.tick(n) and charge CROBOTS cycles
GATEWAY_INTERFACE=CGI/1.1 bin/crystal-robots        # serve the web app (Fossil does this for you)

The easiest way to play is the public site. The compiler is built into the web page. You can provide sources for the various robots and watch them battle it out.

There are a lot of other methods to battle your crystal-robots and each peels back a layer to teach you more about full-stack programming.

Fossil server for contributors

The web app is a Fossil CGI extension: Fossil serves the repository, the docs and the app, and supplies the login. The app replies in Markdown, so it appears inside the repository's own skin.

shards build
scripts/install_extroot.sh /path/to/extroot      # symlinks extroot/crystal-robots -> bin/crystal-robots
fossil server crystal-robots.fossil --extroot /path/to/extroot --port 8080

Then browse to http://localhost:8080/ext/crystal-robots/: pick example robots or paste your own, run a seeded match, watch the replay at a chosen pace (cycles per second, 300 by default, roughly the original curses display), step through its frames drawn in Pikchr with each robot's trail, or run a series of matches for a score table like crobots -m.

To keep a robot, create a wiki page named robot/<name> whose Markdown contains exactly one fenced code block; that block is the robot. It then appears on the overview (with its first paragraph as a description and a "fight" link), in the battle picker, and at /ext/crystal-robots/wiki/<name> with its derivation and checks. Five such robots ship in robots/*.md (hunter, circler, dodger, wallhugger, turret); publish them to a repository's wiki with:

scripts/publish_wiki_robots.sh -R /path/to/crystal-robots.fossil

A CROBOTS rule worth knowing when writing one: a heading change only takes at 50 percent speed or less. Ask for a turn while faster and the drive disengages, so slow down first (the shipped robots show both ways).

Cycles are charged the way the CROBOTS virtual machine did: one per operand fetch, operator, store, branch and statement, two per builtin call, three around a user function call. -l limits those cycles. A rebuild is the deploy: the CGI runs fresh on every request. To put the app in the Fossil menu, paste fossil-skin/mainmenu into Admin, Skins, Main Menu. It mirrors the deployed menu (Agents, Docs and a "Run" entry for this app); merge rather than replace if your skin has other rows. Who may use the app is decided by the repository's user capabilities: reading the overview and examples needs o or h (what anonymous usually has); running battles and parsing needs check-in (i); seeing saved robots needs wiki read (j).

Tournament

/ext/crystal-robots/tournament lets you pick robots (or Check everyone) into a tournament: pool play (round-robin, win +1 / loss -1, a refight on a tie or a no-winner fight) followed by a single-elimination bracket (best of 3, byes for the top seeds) down to one champion. The whole thing is stateless like a battle: every stage's outcome round-trips through the tournament's own link, so it replays exactly and can be shared or resumed from that link alone. Running one needs check-in (i), the same permission battles need.

Self-hosted server without Fossil

Planned: bin/crystal-robots -p 8080 will serve the same pages directly.

Compiled to native code with crystal

To setup the environment for your robots, use prelude.cr ...

crystal run --prelude=../src/prelude robot1.cr robot2.cr robot3.cr robot4.cr -- -m 500

Command-line interpretation by crystal-robots

Using the crystal-robots compiler, you can perform battles by running the built-in interpreter ...

bin/crystal-robots -i -m 5 robot1.cr robot2.cr robot3.cr robot4.cr

Compiled to WASM by crystal-robots and executed with wasmer

Support

TODO: Write support instructions here

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