Scrappers v0.1: Mercenary Programmers

Question

In a desolate, war-torn world, where cities have been overrun by thugs and thieves, civilization has reinvented itself in the form of small, isolated, industrial cooperatives, scattered throughout the previously uninhabited landscape. The existence of these communities is reliant on teams of mercenary workers called "scrappers", who search the untamed territory for valuable materials to sell to the coops. As these materials have grown more scarce, scrapping has become an ever more difficult and dangerous profession. Fragile human workers have mostly been replaced with remote robotic stand-ins, called “bots”, and a typical mercenary is more likely to be a skilled programmer than an armed welder. As the human presence in scrapping has declined, so too has the respect between mercenary groups for one another. Bots are equipped not only to collect scrap, but to defend it, and in some cases take it by force. Bot programmers work tirelessly devising new strategies to outsmart rival scrappers, resulting in increasingly aggressive bots, and yet another danger for humans who venture outside the walls of their communities.

(yeah, the logo gets cropped hilariously)

Welcome to Scrappers!

This is an early version of Scrappers in which scrap collection and factories have not been implemented. It’s basically a “shoot ‘em up”.

You are a mercenary programmer tasked with creating a program to remotely conduct your bots to victory over rival scrapper groups. Your bots are spider-like machines consisting of power and shield generators at their core, surrounded by many appendages equipped with gripping, cutting, and attacking implements. The power generator is capable of producing 12 power units (pu) per tick (a scrapper's unit of time). You are in control of how this power is distributed amongst a bot's three primary needs: movement, shields, and firepower.

Scrapper bots are exceptionally agile machines, and can easily move over, under, and around any obstacles they encounter. Thus, collision is not something that your program needs take into consideration. You are free to allocate all, some, or none of the 12pu available to your bot for movement, as long as you deal in whole numbers. Allocating 0pu to a bot's movement functions would render it immobile. Allocating 2pu would enable a bot to move 2 distance units (du) per tick, 5pu would result in 5du/tick, 11pu would result in 11du/tick, and so on.

Your bots’ shield generators project a bubble of deflective energy around their body. A shield can deflect up to 1 damage before popping, thus leaving your bot exposed until it's shield generator builds enough power to snap the shield back into place. You are free to allocate all, some, or none of the 12pu available to your bot towards it’s shield. Allocating 0pu to a bot's shield means that it will never generate a shield. Allocating 2pu would allow a bot to generate a new shield 2 out of 12 ticks, or once every 6 ticks. 5pu would result in shield regeneration 5 out of every 12 ticks, and so on.

By building up a charge in their welding lasers, your bots can fire damaging beams over short distances with fair accuracy. Like shield generation, your bots’ rate of fire depends on the power allocated to their lasers. Allocating 0pu to a bot's lasers means that it will never fire. Allocating 2pu would allow a bot to fire 2 out of every 12 ticks, and so on. A bot’s laser will travel until it encounters an object or disperses into uselessness, so be mindful of friendly fire. Although your bots are quite accurate, they aren’t perfect. You should expect +/- 2.5 degrees of variance in accuracy. As the laser beam travels, its particles are incrementally deflected by the atmosphere until the beam becomes effectively harmless with enough distance. A laser does 1 damage at point blank range, and 2.5% less damage every bot-length it travels. In other words, the closer you are to your target, the more likely you are to hit it, and the more damage you will cause.

Scrapper bots are autonomous enough to handle basic functions, but rely on you, their programmer, to make them useful as a group. As a programmer, you may issue the following commands for each individual bot:

• MOVE: Specify coordinates towards which a bot will move.
• TARGET: Identify a bot to aim at and fire at when power allocation allows.
• POWER: Redistribute power between movement, shields, and firepower.

Technical Game Details

There are three programs that you'll need to be familiar with. The Game Engine is the heavy lifter and provides a TCP API that the player programs connect to. The player program is what you'll write, and I've provided some examples with binaries here. Finally, the Renderer processes the output from the Game Engine to produce a GIF of the battle.

The Game Engine

You can download the game engine from here. When the game is launched, it will begin listening on port 50000 (currently not configurable) for player connections. Once it receives two player connections, it sends the READY message to the players and begins the game. Player programs send commands to the game via the TCP API. When the game is over, a JSON file named scrappers.json (also, currently not configurable) is created. This is what the renderer uses to create a GIF of the game.

The TCP API

Player programs and the game engine communicate by passing newline-terminated JSON strings back and fourth over a TCP connection. There are just five different JSON messages that can be sent or received.

Ready Message

The READY message is sent from the game to the player programs and is only sent once. This message tells the player program what its player ID (PID) is and provides a list of all the bots in the game. The PID is the only way to determine which Bots are friendly vs enemy. More info on the bot fields below.

{
    "Type":"READY",  // Message type
    "PID":1,         // Player ID
    "Bots":[         // Array of bots
        {
            "Type":"BOT",
            "PID":1,
            "BID":1,
            "X":-592,
            ...
        },
        ...
    ]
}

Bot Message

The BOT message is sent from the game to the player programs and is sent when a bot's attributes change. For instance, when shields are projected, or health changes, a BOT message is sent. The Bot ID (BID) is only unique within a particular player.

{
    "Type":"BOT",   // Message type
    "PID":1,        // Player ID
    "BID":1,        // Bot ID
    "X":-592,       // Current X position
    "Y":-706,       // Current Y position
    "Health":12,    // Current health out of 12
    "Fired":false,  // If the Bot fired this tick
    "HitX":0,       // X position of where the shot landed
    "HitY":0,       // Y position of where the shot landed
    "Scrap":0,      // Future use. Ignore.
    "Shield":false  // If the Bot is currently shielded.
}

Move Message

The MOVE message is a command from the player program to the game (but think of it as a command to a bot). Simply identify the bot you want to move, and the coordinates. It's assumed that you are commanding your own bot, so no PID is necessary.

{
    "Cmd":"MOVE",
    "BID":1,        // Bot ID
    "X":-592,       // Destination X coordinate
    "Y":-706,       // Destination Y coordinate
}

Target Message

The TARGET message tells one of your bots to target some other bot.

{
    "Cmd":"TARGET",
    "BID":1,        // Bot ID
    "TPID":0,       // The PID of the bot being targeted
    "TBID":0,       // The BID of the bot being targeted
}

Power Message

The POWER message reallocates the 12pu available to your bot between movement, firepower, and shields.

{
    "Cmd":"POWER",
    "BID":1,        // Bot ID
    "FPow":4,       // Set fire power
    "MPow":4,       // Set move power
    "SPow":4,       // Set shield power
}

The Competition

If you're brave enough to explore the untamed lands, you'll be entered into a double-elimination tournament against your mercenary peers. Please create an answer for your submission and either paste your code or provide a link to a git repo, gist, etc. Any language is acceptable, but you should assume I know nothing about the language and include instructions for running your program. Create as many submissions as you like, and be sure to give them names!

The sample player programs will be included in the tournament, so I highly recommend testing your bot against them. The tournament will commence roughly two weeks after we get four unique program submissions. Good luck!

--- Winner's Bracket ---

** Contestants will be randomly seeded **
__________________
                  |___________
__________________|           |
                              |___________
__________________            |           |
                  |___________|           |
__________________|                       |
                                          |________________
__________________                        |                |
                  |___________            |                |
__________________|           |           |                |
                              |___________|                |
__________________            |                            |
                  |___________|                            |
__________________|                                        |
                                                           |
--- Loser's Bracket ---                                    |___________
                                                           |
___________                                                |
           |___________                                    |
___________|           |___________                        |
                       |           |                       |
            ___________|           |                       |
                                   |___________            |
___________                        |           |           |
           |___________            |           |___________|
___________|           |___________|           |
                       |                       |
            ___________|            ___________|

Other Important Info

• The game runs at 12 ticks/second, so you will not receive messages more frequently than every 83 milliseconds or so.
• Each bot is 60du in diameter. The shield takes up no additional space. With the +/- 2.5% accuracy, the odds of hitting a bot at a certain distance are represented by this graph:

• The decay of laser damage over distance is represented by this graph:

• A bot's accuracy and laser decay combine to calculate its average damage per shot. That is, the average damage a bot will cause when it fires from a certain distance. Damage per shot is represented by this graph:

• A bot's laser originates half way between the bot's center and its edge. Thus, stacking your bots will result in friendly fire.
• Enemy bots spawn roughly 1440du apart.
• The game ends if 120 ticks (10 seconds) pass without any damage dealt.
• The winner is the player with the most bots, then the most health when the game ends.

Understanding the Rendered Image

• Player 1 is represented by circles and player 2 by hexagons.
• The color of a bot represents its power allocation. More red means more power has been allocated to firing. More blue means more shield. More green means more movement.
• The "hole" in a bot's body represents damage. The larger the hole, the more damage has been taken.
• The white circles surrounding a bot are it's shield. If a bot has a shield at the end of the turn, it is shown. If the shield was popped by taking damage, it is not shown.
• The red lines between bots represent shots taken.
• When a bot is killed, a large red "explosion" is shown.

Answer 1

Extremist (Python 3)

This bot will always devote all of its power to one thing: shielding if it isn't shielded, moving if it is out of position, and firing otherwise. Beats all of the sample bots except death-dish.

import socket, sys, json
from types import SimpleNamespace
s=socket.socket()
s.connect(("localhost",50000))
f=s.makefile()
bots={1:{},2:{}}
def hook(obj):
    if "BID" in obj:
        try:
            bot = bots[obj["PID"]][obj["BID"]]
        except KeyError:
            bot = SimpleNamespace(**obj)
            bots[bot.PID][bot.BID] = bot
        else:
            bot.__dict__.update(obj)
        return bot
    return SimpleNamespace(**obj)
decoder = json.JSONDecoder(object_hook=hook)
PID = decoder.decode(f.readline()).PID
#side effect: .decode fills bots dictionary
def turtle(bot):
    send({"Cmd":"POWER","BID":bot.BID,"FPow":0,"MPow":0,"SPow":12})
    bot.firing = bot.moving = False
def send(msg):
    s.send(json.dumps(msg).encode("ascii")+b"\n")
for bot in bots[PID].values():
    turtle(bot)
target_bot = None
def calc_target_bot():
    ok_bots = []
    for bot2 in bots[(2-PID)+1].values():
        if bot2.Health < 12:
            ok_bots.append(bot2)
    best_bot = (None,2147483647)
    for bot2 in (ok_bots or bots[(2-PID)+1].values()):
        dist = bot_dist(bot, bot2)
        if dist < best_bot[1]:
            best_bot = bot2, dist
    return best_bot[0]
def bot_dist(bot, bot2):
    if isinstance(bot, tuple):
        bot=SimpleNamespace(X=bot[0],Y=bot[1])
    if isinstance(bot2, tuple):
        bot=SimpleNamespace(X=bot[0],Y=bot[1])
    distx = bot2.X - bot.X
    disty = bot2.Y - bot.Y
    return (distx**2+disty**2)**.5
LENGTH_Y = -80
LENGTH_X = 80
line = None
def move(bot, pos):
    bot.firing = False
    bot.moving = True
    send({"Cmd":"POWER","BID":bot.BID,"FPow":0,"MPow":12,"SPow":0})
    send({"Cmd":"MOVE","BID": bot.BID,"X":pos[0],"Y":pos[1]})
def go(bot, line):
    if line != None:
        position = (line[0]+LENGTH_X*(bot.BID-6),line[1]+LENGTH_Y*(bot.BID-6))
        if not close_pos(bot, position, 1.5):
            return True, position
    return False, None
def close_pos(bot, pos, f):
    if abs(bot.X - pos[0]) <= abs(LENGTH_X*f) or \
        abs(bot.Y - pos[1]) <= abs(LENGTH_Y*f):
        return True
def set_line(bot):
    global line
    newline = bot.X - LENGTH_X*(bot.BID - 6), bot.Y - LENGTH_Y*(bot.BID - 6)
    if line == None or bot_dist(line, target_bot) < (bot_dist(newline, target_bot) - 100):
        line = newline
def move_or_fire(bot):
    global target_bot, line
    if not target_bot:
        target_bot = calc_target_bot()
    followline, place = go(bot, line)
    if not target_bot:
        #Game should be over, but just in case ...
        return turtle(bot)
    elif bot_dist(bot, target_bot) > 2000:
        line = None
        position = (target_bot.X, target_bot.Y)
        position = (position[0]+LENGTH_X*(bot.BID-6),position[1]+LENGTH_Y*(bot.BID-6))
        move(bot, position)
    elif followline:
        set_line(bot)
        move(bot, place)
    elif any(close_pos(bot, (bot2.X, bot2.Y), .6) for bot2 in bots[PID].values() if bot != bot2):
        try:
            move(bot, place)
        except TypeError:
            turtle(bot)
        set_line(bot)
        #Let the conflicting bots resolve
    else:
        set_line(bot)
        bot.firing = True
        bot.moving = False
        send({"Cmd":"POWER","BID":bot.BID,"FPow":12,"MPow":0,"SPow":0})
        send({"Cmd":"TARGET","BID": bot.BID,
              "TPID":target_bot.PID,"TBID":target_bot.BID})
def dead(bot):
    del bots[bot.PID][bot.BID]
def parse_message():
    global target_bot
    line = f.readline()
    if not line:
        return False
    bot = decoder.decode(line)
    assert bot.Type == "BOT"
    del bot.Type
    if bot.PID == PID:
        if bot.Health <= 0:
            dead(bot)
        elif not bot.Shield:
            turtle(bot)
        else:
            move_or_fire(bot)
    elif target_bot and (bot.BID == target_bot.BID):
        target_bot = bot
        if target_bot.Health <= 0:
            target_bot = None
            dead(bot)
            for bot in bots[PID].values():
                if bot.firing or bot.moving:
                    move_or_fire(bot)
    elif bot.Health <= 0:
        dead(bot)
    assert bot.Health > 0 or bot.BID not in bots[bot.PID]
    return True
while parse_message():
    pass

Answer 2

Less Reckless (Go)

go run main.go

Originally, I planned to slightly modify the Reckless Abandon sample program so that bots would not fire if a friendly bot was in the way. I ended up with bots that pick new targets when a friend is in the way, which I guess is better. It'll beat the first two programs.

The code isn't perfect. The logic to determine if a shot is clear uses some pretty random guesswork.

There doesn't seem to be a mechanism to target "nobody". That might be a good feature to add.

The TCP API is nice in that any language can play, but it also means a lot of boilerplate code. If I wasn't familiar with the language the sample bots were written in, I probably wouldn't have been motivated to play around with this. A collection of boilerplate samples in various languages would be a great addition to your other git repos.

( most of the following code is copy/paste from one of the sample bots )

package main

import (
    "bufio"
    "encoding/json"
    "flag"
    "io"
    "log"
    "math"
    "math/rand"
    "net"
    "time"
)

const (
    MaxHealth int = 12
    BotSize float64 = 60
)

var (
    // TCP connection to game.
    gameConn net.Conn
    // Queue of incoming messages
    msgQueue chan MsgQueueItem
)

// MsgQueueItem is a simple vehicle for TCP
// data on the incoming message queue.
type MsgQueueItem struct {
    Msg string
    Err error
}

// Command contains all the fields that a player might
// pass as part of a command. Fill in the fields that
// matter, then marshal into JSON and send.
type Command struct {
    Cmd  string
    BID  int
    X    int
    Y    int
    TPID int
    TBID int
    FPow int
    MPow int
    SPow int
}

// Msg is used to unmarshal every message in order
// to check what type of message it is.
type Msg struct {
    Type string
}

// BotMsg is used to unmarshal a BOT representation
// sent from the game.
type BotMsg struct {
    PID, BID   int
    X, Y       int
    Health     int
    Fired      bool
    HitX, HitY int
    Scrap      int
    Shield     bool
}

// ReadyMsg is used to unmarshal the READY
// message sent from the game.
type ReadyMsg struct {
    PID  int
    Bots []BotMsg
}

// Create our game data storage location
var gdb GameDatabase

func main() {

    var err error
    gdb = GameDatabase{}
    msgQueue = make(chan MsgQueueItem, 1200)

    // What port should we connect to?
    var port string
    flag.StringVar(&port, "port", "50000", "Port that Scrappers game is listening on.")
    flag.Parse()

    // Connect to the game
    gameConn, err = net.Dial("tcp", ":"+port)
    if err != nil {
        log.Fatalf("Failed to connect to game: %v\n", err)
    }
    defer gameConn.Close()

    // Process messages off the incoming message queue
    go processMsgs()

    // Listen for message from the game, exit if connection
    // closes, add message to message queue.
    reader := bufio.NewReader(gameConn)
    for {
        msg, err := reader.ReadString('\n')
        if err == io.EOF {
            log.Println("Game over (connection closed).")
            return
        }
        msgQueue <- MsgQueueItem{msg, err}
    }
}

func runStrategy() {

    // LESS RECKLESS ABANDON
    // - For three seconds, all bots move as fast as possible in a random direction.
    // - After three seconds, split power between speed and firepower.
    // - Loop...
    //     - Identify the enemy bot with the lowest health.
    //     - If a friendly bot is in the way, pick someone else.
    //     - If there's a tie, pick the one closest to the group.
    //     - Everybody moves towards and targets the bot.

    var myBots []*GDBBot

    // Move quickly in random direction.
    // Also, might as well get a shield.
    myBots = gdb.MyBots()
    for _, bot := range myBots {
        send(bot.Power(0, 11, 1))
        radians := 2.0 * math.Pi * rand.Float64()
        x := bot.X + int(math.Cos(radians)*999)
        y := bot.Y + int(math.Sin(radians)*999)
        send(bot.Move(x, y))
    }

    // Wait three seconds
    time.Sleep(3 * time.Second)

    // Split power between speed and fire
    for _, bot := range myBots {
        send(bot.Power(6, 6, 0))
    }

    for { // Loop indefinitely

        // Find a target

        candidates := gdb.TheirBots()

        // Order by health
        reordered := true
        for reordered {
            reordered = false
            for n:=1; n<len(candidates); n++ {
                if candidates[n].Health < candidates[n-1].Health {
                    temp := candidates[n-1]
                    candidates[n-1] = candidates[n]
                    candidates[n] = temp
                    reordered = true
                }
            }
        }

        // Order by closeness

        // My swarm position is...
        ttlX, ttlY := 0, 0
        myBots = gdb.MyBots() // Refresh friendly bot list
        for _, bot := range myBots {
            ttlX += bot.X
            ttlY += bot.Y
        }
        avgX := ttlX / len(myBots)
        avgY := ttlY / len(myBots)

        // Sort
        reordered = true
        for reordered {
            reordered = false
            for n:=1; n<len(candidates); n++ {
                thisDist := distance(avgX, avgY, candidates[n].X, candidates[n].Y)
                lastDist := distance(avgX, avgY, candidates[n-1].X, candidates[n-1].Y)
                if thisDist < lastDist {
                    temp := candidates[n-1]
                    candidates[n-1] = candidates[n]
                    candidates[n] = temp
                    reordered = true
                }
            }
        }

        // For all my bots, try to find the weakest enemy that my bot has a clear shot at
        myBots = gdb.MyBots()
        for _, bot := range myBots {
            for _, enemy := range candidates {

                clear := clearShot(bot, enemy)
                if clear {

                    // Target and move towards
                    send(bot.Target(enemy))
                    send(bot.Follow(enemy))
                    break
                }
                log.Println("NO CLEAR SHOT")
            }
        }

        time.Sleep(time.Second / 24)
    }
}

func clearShot(bot, enemy *GDBBot) bool {

    deg45rad := math.Pi*45/180
    deg30rad := math.Pi*30/180
    deg15rad := math.Pi*15/180
    deg5rad := math.Pi*5/180

    myBots := gdb.MyBots()
    enmyAngle := math.Atan2(float64(enemy.Y-bot.Y), float64(enemy.X-bot.X))

    for _, friend := range myBots {

        dist := distance(bot.X, bot.Y, friend.X, friend.Y)
        angle := math.Atan2(float64(friend.Y-bot.Y), float64(friend.X-bot.X))
        safeAngle := angle

        if dist < BotSize*3 {
            safeAngle = deg45rad/2
        } else if dist < BotSize*6 {
            safeAngle = deg30rad/2
        } else if dist < BotSize*9 {
            safeAngle = deg15rad/2
        } else {
            safeAngle = deg5rad/2
        }

        if angle <= enmyAngle+safeAngle &&  angle >= enmyAngle-safeAngle {
            return false
        }
    }

    return true
}

func processMsgs() {

    for {
        queueItem := <-msgQueue
        jsonmsg := queueItem.Msg
        err := queueItem.Err

        if err != nil {
            log.Printf("Unknown error reading from connection: %v", err)
            continue
        }

        // Determine the type of message first
        var msg Msg
        err = json.Unmarshal([]byte(jsonmsg), &msg)
        if err != nil {
            log.Printf("Failed to marshal json message %v: %v\n", jsonmsg, err)
            return
        }

        // Handle the message type

        // The READY message should be the first we get. We
        // process all the data, then kick off our strategy.
        if msg.Type == "READY" {

            // Unmarshal the data
            var ready ReadyMsg
            err = json.Unmarshal([]byte(jsonmsg), &ready)
            if err != nil {
                log.Printf("Failed to marshal json message %v: %v\n", jsonmsg, err)
            }

            // Save our player ID
            gdb.PID = ready.PID
            log.Printf("My player ID is %v.\n", gdb.PID)

            // Save the bots
            for _, bot := range ready.Bots {
                gdb.InsertUpdateBot(bot)
            }

            // Kick off our strategy
            go runStrategy()

            continue
        }

        // The BOT message is sent when something about a bot changes.
        if msg.Type == "BOT" {

            // Unmarshal the data
            var bot BotMsg
            err = json.Unmarshal([]byte(jsonmsg), &bot)
            if err != nil {
                log.Printf("Failed to marshal json message %v: %v\n", jsonmsg, err)
            }

            // Update or add the bot
            gdb.InsertUpdateBot(bot)

            continue
        }

        // If we've gotten to this point, then we
        // were sent a message we don't understand.
        log.Printf("Recieved unknown message type \"%v\".", msg.Type)
    }
}

///////////////////
// GAME DATABASE //
///////////////////

// GameDatabase stores all the data
// sent to us by the game.
type GameDatabase struct {
    Bots []GDBBot
    PID  int
}

// GDBBot is the Bot struct for the Game Database.
type GDBBot struct {
    BID, PID int
    X, Y     int
    Health   int
}

// InserUpdateBot either updates a bot's info,
// deletes a dead bot, or adds a new bot.
func (gdb *GameDatabase) InsertUpdateBot(b BotMsg) {

    // If this is a dead bot, remove and ignore
    if b.Health <= 0 {

        for i := 0; i < len(gdb.Bots); i++ {
            if gdb.Bots[i].BID == b.BID && gdb.Bots[i].PID == b.PID {
                gdb.Bots = append(gdb.Bots[:i], gdb.Bots[i+1:]...)
                return
            }
        }
        return
    }

    // Otherwise, update...
    for i, bot := range gdb.Bots {
        if b.BID == bot.BID && b.PID == bot.PID {
            gdb.Bots[i].X = b.X
            gdb.Bots[i].Y = b.Y
            gdb.Bots[i].Health = b.Health
            return
        }
    }

    // ... or Add
    bot := GDBBot{}
    bot.PID = b.PID
    bot.BID = b.BID
    bot.X = b.X
    bot.Y = b.Y
    bot.Health = b.Health
    gdb.Bots = append(gdb.Bots, bot)
}

// MyBots returns a pointer array of GDBBots owned by us.
func (gdb *GameDatabase) MyBots() []*GDBBot {
    bots := make([]*GDBBot, 0)
    for i, bot := range gdb.Bots {
        if bot.PID == gdb.PID {
            bots = append(bots, &gdb.Bots[i])
        }
    }
    return bots
}

// TheirBots returns a pointer array of GDBBots NOT owned by us.
func (gdb *GameDatabase) TheirBots() []*GDBBot {
    bots := make([]*GDBBot, 0)
    for i, bot := range gdb.Bots {
        if bot.PID != gdb.PID {
            bots = append(bots, &gdb.Bots[i])
        }
    }
    return bots
}

// Move returns a command struct for movement.
func (b *GDBBot) Move(x, y int) Command {
    cmd := Command{}
    cmd.Cmd = "MOVE"
    cmd.BID = b.BID
    cmd.X = x
    cmd.Y = y
    return cmd
}

// Follow is a convenience function which returns a
// command stuct for movement using a bot as a destination.
func (b *GDBBot) Follow(bot *GDBBot) Command {
    cmd := Command{}
    cmd.Cmd = "MOVE"
    cmd.BID = b.BID
    cmd.X = bot.X
    cmd.Y = bot.Y
    return cmd
}

// Target returns a command struct for targeting a bot.
func (b *GDBBot) Target(bot *GDBBot) Command {
    cmd := Command{}
    cmd.Cmd = "TARGET"
    cmd.BID = b.BID
    cmd.TPID = bot.PID
    cmd.TBID = bot.BID
    return cmd
}

// Power returns a command struct for seting the power of a bot.
func (b *GDBBot) Power(fire, move, shield int) Command {
    cmd := Command{}
    cmd.Cmd = "POWER"
    cmd.BID = b.BID
    cmd.FPow = fire
    cmd.MPow = move
    cmd.SPow = shield
    return cmd
}

////////////////////
// MISC FUNCTIONS //
////////////////////

// Send marshals a command to JSON and sends to the game.
func send(cmd Command) {
    bytes, err := json.Marshal(cmd)
    if err != nil {
        log.Fatalf("Failed to mashal command into JSON: %v\n", err)
    }
    bytes = append(bytes, []byte("\n")...)
    gameConn.Write(bytes)
}

// Distance calculates the distance between two points.
func distance(xa, ya, xb, yb int) float64 {
    xdist := float64(xb - xa)
    ydist := float64(yb - ya)
    return math.Sqrt(math.Pow(xdist, 2) + math.Pow(ydist, 2))
}

Answer 3

Trigger Happy - Java 8

Trigger Happy is a simple evolution of my original, but no longer viable, Bombard bot. It is a very simple bot that will simply fire on the currently targeted enemy if there is a clear shot, otherwise performs a random walk to try to get into a better position. All the time attempting to have a shield.

However, for all its simplicity it is very effective. And will readily destroy the sample bots.

Note, there are multiple bugs with the bot such as will sometimes fire even when not a clear shot and may not maintain a shield... but it is still effective so will just submit this entry as-is

Death-dish vs Trigger Happy

Code as follows:

import java.io.IOException;
import java.io.InputStream;
import java.io.PrintStream;
import java.net.Inet4Address;
import java.net.InetAddress;
import java.net.Socket;
import java.util.HashMap;
import java.util.List;
import java.util.stream.Collectors;

//import visual.Viewer;

public class TriggerHappy {

  static final int BOT_RADIUS = 30;
private static final double WALK_MAX_DIRECTION_CHANGE = Math.PI/3;
  static Bot targetedBot;

  enum BotState
  {
    INIT,
    RANDOM_WALK,
    FIRING,
    SHIELDING,
    DEAD,
    END
  }

  enum Power
  {
    MOVE,
    FIRE,
    SHIELD
  }


  private static PrintStream out;
private static List<Bot> enemyBots;
private static List<Bot> myBots;
//private static Viewer viewer;

  public static void main(String[] args) throws Exception
  {
    InetAddress localhost = Inet4Address.getLocalHost();
    Socket socket = new Socket(localhost, 50000);
    InputStream is = socket.getInputStream();
    out = new PrintStream(socket.getOutputStream());

    // read in the game configuration
    String line = readLine(is);
    Configuration config = new Configuration(line);
  //  viewer = new Viewer(line);

    myBots = config.bots.values().stream().filter(b->b.playerId==config.playerId).collect(Collectors.toList());
    enemyBots = config.bots.values().stream().filter(b->b.playerId!=config.playerId).collect(Collectors.toList());


    // set initial target
    targetedBot = enemyBots.get(enemyBots.size()/2);
    myBots.forEach(bot->target(bot,targetedBot));

    for (line = readLine(is);line!=null;line = readLine(is))
    {
//      viewer.update(line);
      // read in next bot update message from server
      Bot updatedBot = new Bot(line);
      Bot currentBot = config.bots.get(updatedBot.uniqueId);
      currentBot.update(updatedBot);

      // check for bot health
      if (currentBot.health<1)
      {
        // remove dead bots from lists
        currentBot.state=BotState.DEAD;
        if (currentBot.playerId == config.playerId)
        {
          myBots.remove(currentBot);
        }
        else
        {
          enemyBots.remove(currentBot);

          // change target if the targetted bot is dead
          if (currentBot == targetedBot)
          {
            if (enemyBots.size()>0)
            {
              targetedBot = enemyBots.get(enemyBots.size()/2);
              myBots.forEach(bot->target(bot,targetedBot));
            }
            // no more enemies... set bots to end state
            else
            {
              myBots.forEach(bot->bot.state = BotState.END);
            }
          }
        }
      }
      else
      {
          // ensure our first priority is shielding
          if (!currentBot.shield && currentBot.state!=BotState.SHIELDING)
          {
              currentBot.state=BotState.SHIELDING;
              shield(currentBot);
          }
          else
          {
              // not game end...
              if (currentBot.state != BotState.END)
              {
                // command to fire if we have a clear shot
                if (clearShot(currentBot))
                {
                    currentBot.state=BotState.FIRING;
                    fire(currentBot);
                }
                // randomly walk to try and get into a better position to fire
                else
                {
                    currentBot.state=BotState.RANDOM_WALK;
                    currentBot.dir+=Math.random()*WALK_MAX_DIRECTION_CHANGE - WALK_MAX_DIRECTION_CHANGE/2;
                    move(currentBot, (int)(currentBot.x+Math.cos(currentBot.dir)*100), (int) (currentBot.y+Math.sin(currentBot.dir)*100));
                }

              }
          }
      }
    }
    is.close();
    socket.close();
  }

// returns true if there are no friendly bots in firing line... mostly
private static boolean clearShot(Bot originBot)
{

    double originToTargetDistance = originBot.distanceFrom(targetedBot);
    for (Bot bot : myBots)
    {
        if (bot != originBot)
        {
            double x1 = originBot.x - bot.x;
            double x2 = targetedBot.x - bot.x;
            double y1 = originBot.y - bot.y;
            double y2 = targetedBot.y - bot.y;
            double dx = x2-x1;
            double dy = y2-y1;
            double dsquared = dx*dx + dy*dy;
            double D = x1*y2 - x2*y1;
            if (1.5*BOT_RADIUS * 1.5*BOT_RADIUS * dsquared > D * D && bot.distanceFrom(targetedBot) < originToTargetDistance)
            {
                return false;
            }
        }
    }

    return true;

}


  static class Bot
  {
    int playerId;
    int botId;
    int x;
    int y;
    int health;
    boolean fired;
    int hitX;
    int hitY;
    double dir = Math.PI*2*Math.random();
    boolean shield;
    int uniqueId;
    BotState state = BotState.INIT;
    Power power = Power.SHIELD;


    Bot(String line)
    {
      String[] tokens = line.split(",");
      playerId = extractInt(tokens[1]);
      botId = extractInt(tokens[2]);
      x = extractInt(tokens[3]);
      y = extractInt(tokens[4]);
      health = extractInt(tokens[5]);
      fired = extractBoolean(tokens[6]);
      hitX = extractInt(tokens[7]);
      hitY = extractInt(tokens[8]);
      shield = extractBoolean(tokens[10]);
      uniqueId = playerId*10000+botId;
    }

    Bot()
    {
    }

    double distanceFrom(Bot other)
    {
        return distanceFrom(new Point(other.x,other.y));
    }

    double distanceFrom(Point other)
    {
        double deltaX = x - other.x;
        double deltaY = y - other.y;
        return Math.sqrt(deltaX * deltaX + deltaY * deltaY);
    }

    void update(Bot other)
    {
      x = other.x;
      y = other.y;
      health = other.health;
      fired = other.fired;
      hitX = other.hitX;
      hitY = other.hitY;
      shield = other.shield;
    }
  }

  static class Configuration
  {
    BotState groupState = BotState.INIT;
    HashMap<Integer,Bot> bots = new HashMap<>();
    boolean isOpponentInitiated;
    int playerId;

    Configuration(String line) throws Exception
    {
      String[] tokens = line.split("\\[");
      playerId = extractInt(tokens[0].split(",")[1]);

      for (String token : tokens[1].split("\\|"))
      {
        Bot bot = new Bot(token);
        bots.put(bot.uniqueId,bot);
      }
    }
  }

  /**
   * Reads a line of text from the input stream. Blocks until a new line character is read.
   * NOTE: This method should be used in favor of BufferedReader.readLine(...) as BufferedReader buffers data before performing
   * text line tokenization. This means that BufferedReader.readLine() will block until many game frames have been received. 
   * @param in a InputStream, nominally System.in
   * @return a line of text or null if end of stream.
   * @throws IOException
   */
  static String readLine(InputStream in) throws IOException
  {
     StringBuilder sb = new StringBuilder();
     int readByte = in.read();
     while (readByte>-1 && readByte!= '\n')
     {
        sb.append((char) readByte);
        readByte = in.read();
     }
     return readByte==-1?null:sb.toString().replace(",{", "|").replaceAll("}", "");

  }

  final static class Point
  {
    public Point(int x2, int y2) {
        x=x2;
        y=y2;
    }
    int x;
    int y;
  }

  public static int extractInt(String token)
  {
    return Integer.parseInt(token.split(":")[1]);
  }

  public static boolean extractBoolean(String token)
  {
    return Boolean.parseBoolean(token.split(":")[1]);
  }

  static void distributePower(Bot bot, int fire, int move, int shield)
  {
    out.println("{\"Cmd\":\"POWER\",\"BID\":"+bot.botId+",\"FPow\":"+fire+",\"MPow\":"+move+",\"SPow\":"+shield+"}");
//  viewer.distributePower(bot.botId, fire, move, shield);
  }

  static void shield(Bot bot)
  {
    distributePower(bot,0,0,12);
    bot.power=Power.SHIELD;
  }

  static void move(Bot bot, int x, int y)
  {
    distributePower(bot,0,12,0);
    out.println("{\"Cmd\":\"MOVE\",\"BID\":"+bot.botId+",\"X\":"+x+",\"Y\":"+y+"}");
  }
  static void target(Bot bot, Bot target)
  {
    out.println("{\"Cmd\":\"TARGET\",\"BID\":"+bot.botId+",\"TPID\":"+target.playerId+",\"TBID\":"+target.botId+"}");
  }

  static void fire(Bot bot)
  {
    distributePower(bot,12,0,0);
    bot.power=Power.FIRE;
  }
}

To compile: javac TriggerHappy.java

To run: java TriggerHappy