Question 1

What is thebotslam?

Accepted Answer

thebotslam is a programming game you play in your web browser. You build robots from parts, write the programs that control them, and send them into team games against other players' bots. You don't steer anything during a match: your code makes every decision.

Question 2

Do I need to know how to code to play?

Accepted Answer

No. thebotslam is made for first-time coders as much as for experienced programmers. The Tutorial walks you through writing your first robot's brain in Python, a few lines at a time, with no experience needed. If you'd rather not type code at all, you can start with Blocks, which you drag together like Scratch.

Question 3

Is thebotslam free? What costs money?

Accepted Answer

Making an account is free, and so is building machines, writing code, running every test match you like, and playing ladder and friendly matches against other builders. Tournaments are $5 a team, and the winner takes 80% of the pot. If fewer than two teams enter, every fee is refunded.

Question 4

Do I need an account, and how do I make one?

Accepted Answer

You can look around without one, but you need a free account to save machine designs, build bots, and play against other builders. Click Log in at the top right, then Create an account. You pick a username and a password, and you can add an email address if you want sign-in links.

Question 5

Where are my designs, bots and code saved?

Accepted Answer

Your machine designs, the bots built from them, and your teams are kept under your account on thebotslam's server, so they're there wherever you log in. Your code is different: when you click Save in Brain code, it's saved as a file on your own computer, never on thebotslam's server.

Question 6

Which browser should I use, and do I need to install anything?

Accepted Answer

There's nothing to install: thebotslam runs in your web browser. Chrome and Edge give you the smoothest experience, because they can save your code straight back to the same file on your computer each time. In other browsers, saving downloads a fresh copy of the file instead.

Question 7

How does the tutorial work?

Accepted Answer

Click Tutorial in the menu bar. In about 20 minutes, it walks you through building a robot's machine from parts, writing its brain in Python a few lines at a time, and watching it find and hit a target in a test. A panel tells you what to do at each step, and a ring shows you where to click. No coding experience is needed.

Question 8

Can I use feet and pounds instead of metres and kilograms?

Accepted Answer

Yes. You choose Metric (m, kg, m/s) or Imperial (ft, lb, ft/s) when you create your account, and you can change it any time in Profile. Each program also says which units it's written in: the units button above the Brain code editor shows it, and clicking it switches between metric and imperial.

Question 9

What are the Factory, Brain code, Arena and League tabs for?

Accepted Answer

The tabs along the top follow the order you'll use them. In the Factory you build a robot's machine from parts. In Brain code you write its program and test it. The Arena is where matches play and you watch them. The League is where you play other builders, on the ladder and in tournaments.

Question 10

How do I get my first bot into a match?

Accepted Answer

Save a design in the Factory, build a bot from it in Brain code, and write its program. Run a free test match in Brain code's Test arena first. When it works, open the League's Ladder with that program open in Brain code, tick the games to enter, and click Submit Brain code bot: the server plays it in rated matches by itself.

Question 11

How do I build a bot in the Factory?

Accepted Answer

Open the Factory, drag a chassis and the sensors and tools you want from Stock parts onto the Build platform, type a design name and click Save design. Then build a bot from it: click Build next to the design in the Designs tab (or + bot under it in Brain code) and give the bot a name. Saving needs an account, so log in first.

Question 12

What's the difference between a design, a bot and a team?

Accepted Answer

A design is a machine layout: a chassis, an engine, a ROM size and a part on each mount. A bot is built from a design and has a name of its own. You load one of your programs into it. A team is a named group of your bots, and teams are what you enter into matches.

Question 13

Which chassis should I pick for which terrain?

Accepted Answer

Pick wheels for speed on open ground, tracks for a steady all-rounder, legs to cross boulder fields and steep slopes, and a flier to get over boulders and shoot down past blocks' edges. Boulder fields stop tracks and wheels completely. Legs cross them at half speed, and fliers get over them from 3 m up. The Factory's Chassis shelf has a tab for each kind (Flying, Tracked, Wheeled, Legs), and each chassis's hover panel gives its numbers.

Question 14

How many parts can my bot carry?

Accepted Answer

Each chassis has a fixed number of mounts, and each mount holds one part: light, medium and heavy tracked, wheeled and walking chassis have 3, 6 and 11, and a drone has one. Wheeled chassis and the hopper can also only carry a set weight of parts. On other chassis there's no weight limit, but every part you add slows the bot down.

Question 15

What do the sensors do?

Accepted Answer

Sensors are how your program learns about the world: the scanner (SCN-1) finds things around the bot, and the rangefinder (RNG-1) measures how far away they are. GPS and radios say where the bot is, radios also talk to teammates, and other sensors find fliers or tell you which way a hit came from. Hover over any sensor in the Factory to see exactly what it reads and how far it reaches.

Question 16

Which weapon should I start with?

Accepted Answer

Start with the WPN-1 pulse laser. It's on the Factory's starting machine next to a scanner. It hits the moment it fires, along a bearing you choose, and never runs out of ammunition, so it's the easiest weapon to get working. Once your bot finds and hits targets reliably, try rockets, mortars or missiles for longer range and for targets the laser can't reach.

Question 17

Which engine and ROM should my bot have?

Accepted Answer

Every chassis comes with the small engine, ENG-S. That's fine for a light bot, but a loaded medium or heavy chassis needs ENG-M or ENG-L to stay quick. The ROM (ROM-S, ROM-M or ROM-L) only sets how long your program can be. It doesn't give your bot more speed or thinking time, so keep ROM-S until your program outgrows it.

Question 18

Can I change a bot after I've built it?

Accepted Answer

Yes. A bot always has the machine its design has, so to change its parts, put the design back on the Factory's platform, change it and save it under the same name. Every bot built from that design gets the new machine. You can also rename a bot, load a different program into it, or scrap it.

Question 19

Which programming languages can I write my bot's brain in?

Accepted Answer

You can use nine: Python, JavaScript, C++ (Arduino), Java, C#, Lua, BASIC, Assembly and Blocks (Scratch-style, no typing). You pick one in the League list above the editor in Brain code. Whichever you pick, your program is compiled to the same small bot CPU, so every bot controls its parts the same way.

Question 20

Which language should I pick if I'm new to coding?

Accepted Answer

Python is a good first choice: it reads almost like English, and the hands-on tutorial teaches it step by step. If you'd rather not type at all, pick Blocks: you snap Scratch-style blocks together, and Brain code shows you the same program in Python as you go. BASIC is another easy start, with short commands like DRIVE 1 and FIRE B.

Question 21

Is it real Python? Which parts of Python can I use?

Accepted Answer

It's a subset of Python 3: what it keeps has the same syntax and meaning as real Python, but it compiles to a tiny robot CPU, so some things are left out. You get numbers, if/while/for, functions, and fixed-size lists. You don't get strings (except in log()), classes, dicts, tuples or other modules. The other text languages (JavaScript, Lua, C++, Java, C#) are subsets in the same way.

Question 22

Does my choice of language make my bot faster or slower?

Accepted Answer

Not by much, on purpose. Compiled code costs more than hand-written assembly, so every compiled language gets a bigger CPU: twice assembly's cycles per tick and four times its memory. The budgets are measured so that a bot can do about as much in any league. And on the League ladder you're only rated against bots in your own language, so you never race a faster language for rating.

Question 23

What is the bot CPU, and why is there an assembly league?

Accepted Answer

Every bot's brain runs on the same small CPU: 32-bit words, eight registers, about 50 instructions, and a fixed, documented cycle cost for each one. Every language compiles down to its instructions. The Assembly league lets you skip the compiler and write those instructions yourself, so every cycle and register is yours.

Question 24

Can I use libraries, imports, strings or random numbers in my bot's code?

Accepted Answer

No outside libraries: the only thing you can import is the game's own bot module (in C++, Bot.h), which gives you your parts, cpu and wait. There are no strings except a log() line's text, and no random numbers, because the same program on the same match must always play the same way. Everything else your bot needs, you write yourself.

Question 25

How do the cycle, ROM and RAM limits on my bot's code work?

Accepted Answer

Your bot's CPU runs a fixed number of cycles each tick (512 in the compiled leagues, 256 in assembly), at 20 ticks a second. If your code runs out of cycles, the tick ends wherever it is and carries on next tick with readings a tick old. Your compiled program must also fit the ROM (4,096 words in the compiled leagues) and its variables the RAM (1,024 words); if it doesn't, it won't compile.

Question 26

What happens when my bot's code has a compile error?

Accepted Answer

Brain code checks your program as you type. If something's wrong, the status line under the editor shows ✗ and the number of errors, each error is listed with its line number, and that line's number is marked in the editor. Click an error to jump to its line. A program that doesn't compile can't be submitted to the League until you fix it.

Question 27

Can I write my bot's code in my own editor or IDE?

Accepted Answer

Yes. Download your language's API stubs from the API tab in Brain code: they declare every part's class, property and method for each language, with the same docs as Brain code's Reference, so your editor gives you autocomplete, hover docs and type checking. Write your code there, then open the file in Brain code with Open file… to test it and play.

Question 28

How does my program talk to my bot's parts?

Accepted Answer

Every part on your bot sits on a numbered channel: the chassis is always 0, and mounted parts follow in mount order. Your program connects to each part once, at the top (in Python, scanner = Scanner(1)), then sets its commands and reads its readings. Commands go out, and fresh readings come in, each time your program calls wait().

Question 29

How do ticks, wait() and CPU cycles work in my bot's program?

Accepted Answer

A match runs in ticks, 20 a second. Your program runs once from the top and usually loops forever; each call to wait() ends the tick: your commands go out, the rest of the tick's CPU time is given up, and fresh readings come in. Each tick your CPU has a fixed number of cycles (512 in the compiled-language leagues, 256 in assembly), and every line of code costs some of them.

Question 30

Why does my bot just sit there and do nothing?

Accepted Answer

Most often the program never calls wait(), so its commands never go out, or a part is connected on the wrong channel, so it reads 0 and ignores commands. Check the messages under the editor in Brain code first: compile errors and channel problems show there. Then add log() lines and read the bot's log during a test run.

Question 31

How do I make my bot turn to a heading and drive somewhere?

Accepted Answer

Set chassis.forward (throttle, −1 to 1) and chassis.turn (turn rate, −1 to 1, positive turns left). The chassis only drives the way it faces, so to go somewhere you turn toward it and drive. Steer by the difference between the bearing you want and chassis.heading, wrapped into −180..180 and divided by 45.

Question 32

How do I find enemies with the scanner?

Accepted Answer

The scanner looks along a 30° arc that you point with scanner.sense, and reports up to four contacts within 30 m as bearings. Sweep the arc round until scanner.ping(0) is true, then keep it pointed at scanner.bearing(0). The scanner gives no distance and can't tell an enemy from a teammate or an obstacle, so your code has to work that out.

Question 33

How do I aim and fire my bot's laser?

Accepted Answer

Call laser.fire(b) with a field bearing b, usually a scanner contact's scanner.bearing(0). The laser sits on a turret that turns to that bearing instantly, whichever way the chassis faces, and fires once. It only fires when laser.ready is true: after each shot it cools down for 10 ticks (half a second).

Question 34

How do I keep my bot from driving into walls and obstacles?

Accepted Answer

Carry a rangefinder (RNG-1) and point it ahead with rangefinder.bearing = chassis.heading: rangefinder.range tells you how far the first wall, block or bot is, up to 30 m. Turn away when it gets close. A GPS helps too: if you're at full throttle but your position hardly changes, you're pushing against something, so back off.

Question 35

How does my bot know when it's been hit, and how much health it has left?

Accepted Answer

chassis.hull is your bot's health: its hull points left. When it drops, you've been hit; at 0 the bot is out of the match. The hull doesn't say where a hit came from: for that, carry a damage localizer (DMG-1), whose 32 panels report which side was struck.

Question 36

How do my bots share information with their teammates?

Accepted Answer

There are two ways. A radio (RAD-1) sends up to four numbers at a time to every teammate's radio, which gets them the next tick; it also tells each bot where its teammate is. The team notepad is one shared text of up to 1024 characters, built into every bot, that every bot on the team can read and write, and it's kept from one match to the next.

Question 37

Does my code work in metres or feet?

Accepted Answer

Each program has its own units. Without a units line it's metric, and the game gives it every length in metres. Put # units: imperial near the top (in Python) and the game gives it feet instead, both in what it reads and in what it sends. Only lengths and areas change: angles, throttles, turn rates, hull points and times are the same either way.

Question 38

How do I test my bot before a real match?

Accepted Answer

Open Brain code and click the Test arena tab above the editor. Drag your bot (and something for it to fight) from the list on the left onto the field, choose a Game, and click Run test. The match plays in the Arena, where you can watch it, step through it and read each bot's log. Test matches are free.

Question 39

How do I see what my bot's program is doing?

Accepted Answer

Add log(...) lines to your program: each one writes a line to that bot's log, which shows in Bot logs under the field in the Arena as the match plays. A log costs no cycles and never changes the match, so you can leave as many in as you like. In Brain code, the line under the editor shows whether your code compiled, and Generated assembly shows what it became.

Question 40

What does "CPU fault, rebooting" mean, and how do I fix it?

Accepted Answer

It means your bot's program crashed. The usual causes are an index outside an array or the stack running out. The CPU stalls for a second, then restarts your program from the top with its variables reset. To find the cause, jump to the fault in the Arena's Events and read the bot's Bot logs just before it.

Question 41

How do I replay a match and step through it tick by tick?

Accepted Answer

Every match you watch opens in the Arena, whether it's your own test or a match from the League. Under the field, ⏮ and ⏭ step back and forward one tick (or press ← and →), the timeline jumps to any moment, and the speed slider slows it down. Click any line in Events to replay the moment just before it at half speed.

Question 42

Why did my bot lose, and how do I find out what went wrong?

Accepted Answer

Open the match in the Arena and work back from the end. Events and the marks on the timeline show every hit, bot destroyed and CPU fault; click an event to replay the moment before it at half speed. Bot logs show what your bot's program logged and who damaged it. Then set up the same situation in the Test arena, change your code and run it again.

Question 43

What happens when my program runs out of cycles, and how do I make it faster?

Accepted Answer

Your bot's CPU gets a fixed number of cycles each tick, 20 ticks a second: 256 in the assembly league and 512 in every other league. If they run out, the tick ends wherever your code is, and it carries on next tick with readings a tick old. Nothing crashes, but your bot reacts late. Check your cycles per tick in the Match panel after a test, and do less work each tick.

Question 44

How do I test my bot against other bots, like the house bots?

Accepted Answer

In the Test arena, any of your bots can be an opponent: drag in two different bots, two copies of the same one, or whole teams. To practise against a house bot, give one of your bots a house program: in Brain code, open the Start from… menu and pick House bot: and a name. To play another player's bot, challenge them from the ladder to an unrated friendly match.

Question 45

How does a group of us build and code a bot team?

Accepted Answer

thebotslam saves your bots' code files on your own computer, never on our servers. That makes sharing simple: keep every bot's code files in one folder, track that folder with GitHub, and everyone in your group has their own full copy of all the code. GitHub keeps them in step: each person pulls to get the latest files and pushes their own changes, and it keeps a history of every change, so nothing is ever lost.

Question 46

How many bots can be on a team, and can I mix different machines?

Accepted Answer

A team is a named set of your own bots, and you can mix any machines you like: tracked, wheeled, walkers and fliers side by side, each running its own program. For tournaments, a team plays at most 12 bots, and what matters most is their total weight, because that decides which weight class the team can enter.

Question 47

Can I change my bots' code between matches?

Accepted Answer

Yes, but how depends on where your bots play. On the ladder, submit a new version from Brain code whenever you like: the next rated series uses it. A tournament entry plays with the programs your bots had when you entered. To change them, withdraw the entry (it's refunded) before entries close, 30 minutes before the start, and enter again.

Question 48

What are the game modes, and how do you win each one?

Accepted Answer

There are three games you can play now: Last team standing (the last team with a bot alive wins), Infiltrate (be first to get a bot on the ground in the enemy's circle) and Capture the flag (be first to get the enemy's conch into your own circle). In Infiltrate and Capture the flag, wiping out the enemy wins too. Hide and seek is coming soon.

Question 49

How do I get my bot onto the League ladder?

Accepted Answer

Sign in, open your bot's program in Brain code, then go to League › Ladder and click Submit Brain code bot. Tick the games to enter it in under Enter it in first. The server then pairs your bot with other bots in the same language and game, and plays rated series on its own. You don't need to schedule anything.

Question 50

How are ratings calculated, and what does provisional mean?

Accepted Answer

Ratings use Glicko-2. Everyone starts at 1500 ± 350: the number is how strong you look, and the ± is how sure the system is. Win and your rating goes up; play more and the ± shrinks. A rating is provisional while its ± is above 110, which means few rated games so far, a recent change, or a long break.

Question 51

How do tournaments work, and how do I win and get paid a prize?

Accepted Answer

Tournaments are for teams of your own bots. Each one is at Capture the flag in one weight class, and entry is $5 per team, paid on Stripe's page. Teams play a knockout bracket, best of three, and the winner's owner gets 80% of the entry fees. If fewer than two teams enter, it's called off and every fee is refunded.

Question 52

Can I watch matches live, and can I watch them again afterwards?

Accepted Answer

Yes. Ladder series and friendly matches play in real time: sign in and open League › Live now & challenges to watch one live, with a 3-second delay. Finished matches can be watched again from the Ladder's Rated series and from Friendly matches. Tournament games can be watched once they've been played, with an account or with a link sent to your email.

Frequently asked questions

Getting started

Building bots

Languages and code

Coding your bot

Testing and debugging

Teams and playing together

Matches, ladder and tournaments