path: root/static/src/_posts/2021-04-11-ripple-v2.md

---
title: >-
    Ripple V2: A Better Game
description: >-
    The sequel no one was waiting for!
tags: tech
series: ripple
---

<p>
    <b>Movement:</b> Arrow keys or WASD<br/>
    <b>Jump:</b> Space<br/>
    <b>Goal:</b> Jump as many times as possible without touching a ripple!<br/>
    <br/>
    <b>Press Jump To Begin!</b>
</p>

_Who can make the muddy water clear?<br/>
Let it be still, and it will gradually become clear._

<canvas id="canvas"
        style="border:1px dashed #AAA"
        tabindex=0>
Your browser doesn't support canvas. At this point in the world that's actually
pretty cool, well done!
</canvas>
<button onclick="reset()">(R)eset</button>
<span style="font-size: 2rem; margin-left: 1rem;">Score:
    <span style="font-weight: bold" id="score">0</span>
</span>

<script type="text/javascript">

const palette = [
    "#264653",
    "#2A9D8F",
    "#E9C46A",
    "#F4A261",
    "#E76F51",
];

const width = 800;
const height = 600;

function hypotenuse(w, h) {
    return Math.sqrt(Math.pow(w, 2) + Math.pow(h, 2));
}

let canvas = document.getElementById("canvas");
canvas.width = width;
canvas.height = height;

const whitelistedKeys = {
    "ArrowUp": {},
    "KeyW": {map: "ArrowUp"},
    "ArrowLeft": {},
    "KeyA": {map: "ArrowLeft"},
    "ArrowRight": {},
    "KeyD": {map: "ArrowRight"},
    "ArrowDown": {},
    "KeyS": {map: "ArrowDown"},
    "Space": {},
    "KeyR": {},
};

let keyboard = {};

canvas.addEventListener('keydown', (event) => {
    let keyInfo = whitelistedKeys[event.code];
    if (!keyInfo) return;

    let code = event.code;
    if (keyInfo.map) code = keyInfo.map;

    event.preventDefault();
    keyboard[code] = true;
});

canvas.addEventListener('keyup', (event) => {
    let keyInfo = whitelistedKeys[event.code];
    if (!keyInfo) return;

    let code = event.code;
    if (keyInfo.map) code = keyInfo.map;

    event.preventDefault();
    delete keyboard[code];
});


const C = 700; // scales the overall speed of the radius
const T = 500; // on which tick the radius change becomes linear

/*
    f(x) = sqrt(C*x)                        when x < T
           (C/(2*sqrt(CT)))(x-T) + sqrt(CT) when x >= T

    radius(x) = f(x) + playerRadius;
*/

const F1 = (x) => Math.sqrt(C*x);
const F2C1 = C / (2 * Math.sqrt(C*T));
const F2C2 = Math.sqrt(C * T);
const F2 = (x) => (F2C1 * (x - T)) + F2C2;
const F = (x) => {
    if (x < T) return F1(x);
    return F2(x);
};

class Ripple {

    constructor(id, currTick, x, y, bounces, color) {
        this.id = id;
        this.tick = currTick;
        this.x = x;
        this.y = y;
        this.thickness = Math.pow(bounces+1, 1.25);
        this.color = color;
        this.winner = false;

        this.maxRadius = hypotenuse(x, y);
        this.maxRadius = Math.max(this.maxRadius, hypotenuse(width-x, y));
        this.maxRadius = Math.max(this.maxRadius, hypotenuse(x, height-y));
        this.maxRadius = Math.max(this.maxRadius, hypotenuse(width-x, height-y));
    }

    radius(currTick) {
        const x = currTick - this.tick;
        return F(x) + playerRadius;
    }

    draw(ctx, currTick) {
        ctx.beginPath();
        ctx.arc(this.x, this.y, this.radius(currTick), 0, Math.PI * 2, false);
        ctx.closePath();
        ctx.lineWidth = this.thickness;
        ctx.strokeStyle = this.winner ? "#FF0000" : this.color;
        ctx.stroke();
    }

    canGC(currTick) {
        return this.radius(currTick) > this.maxRadius;
    }
}

const playerRadius = 10;
const playerMoveAccel = 0.5;
const playerMoveDecel = 0.7;
const playerMaxMoveSpeed = 4;
const playerJumpSpeed = 0.08;
const playerMaxHeight = 1;
const playerGravity = 0.01;

class Player{

    constructor(x, y, color) {
        this.x = x;
        this.y = y;
        this.z = 0;
        this.xVelocity = 0;
        this.yVelocity = 0;
        this.zVelocity = 0;
        this.color = color;
        this.falling = false;
        this.lastJumpHeight = 0;
        this.loser = false;
    }

    act() {
        if (keyboard["ArrowUp"]) {
            this.yVelocity = Math.max(-playerMaxMoveSpeed, this.yVelocity - playerMoveAccel);
        } else if (keyboard["ArrowDown"]) {
            this.yVelocity = Math.min(playerMaxMoveSpeed, this.yVelocity + playerMoveAccel);
        } else if (this.yVelocity > 0) {
            this.yVelocity = Math.max(0, this.yVelocity - playerMoveDecel);
        } else if (this.yVelocity < 0) {
            this.yVelocity = Math.min(0, this.yVelocity + playerMoveDecel);
        }

        this.y += this.yVelocity;
        this.y = Math.max(0+playerRadius, this.y);
        this.y = Math.min(height-playerRadius, this.y);

        if (keyboard["ArrowLeft"]) {
            this.xVelocity = Math.max(-playerMaxMoveSpeed, this.xVelocity - playerMoveAccel);
        } else if (keyboard["ArrowRight"]) {
            this.xVelocity = Math.min(playerMaxMoveSpeed, this.xVelocity + playerMoveAccel);
        } else if (this.xVelocity > 0) {
            this.xVelocity = Math.max(0, this.xVelocity - playerMoveDecel);
        } else if (this.xVelocity < 0) {
            this.xVelocity = Math.min(0, this.xVelocity + playerMoveDecel);
        }

        this.x += this.xVelocity;
        this.x = Math.max(0+playerRadius, this.x);
        this.x = Math.min(width-playerRadius, this.x);

        let jumpHeld = keyboard["Space"];

        if (jumpHeld && !this.falling && this.z < playerMaxHeight) {
            this.lastJumpHeight = 0;
            this.zVelocity = playerJumpSpeed;
        } else {
            this.zVelocity = Math.max(-playerJumpSpeed, this.zVelocity - playerGravity);
            this.falling = this.z > 0;
        }

        let prevZ = this.z;
        this.z = Math.max(0, this.z + this.zVelocity);
        this.lastJumpHeight = Math.max(this.z, this.lastJumpHeight);
    }

    draw(ctx) {
        let y = this.y - (this.z * 40);
        let radius = playerRadius * (this.z+1)

        // draw main
        ctx.beginPath();
        ctx.arc(this.x, y, radius, 0, Math.PI * 2, false);
        ctx.closePath();
        ctx.lineWidth = 0;
        ctx.fillStyle = this.color;
        ctx.fill();
        if (this.loser) {
            ctx.strokeStyle = '#FF0000';
            ctx.lineWidth = 2;
            ctx.stroke();
        }

        // draw shadow, if in the air
        if (this.z > 0) {
            let radius = Math.max(0, playerRadius * (1.2 - this.z));
            ctx.beginPath();
            ctx.arc(this.x, this.y, radius, 0, Math.PI * 2, false);
            ctx.closePath();
            ctx.lineWidth = 0;
            ctx.fillStyle = this.color+"33";
            ctx.fill();
        }
    }
}

class Game {

    constructor(canvas, scoreEl) {
        this.currTick = 0;
        this.player = new Player(width/2, height/2, palette[0]);
        this.state = 'play';
        this.score = 0;
        this.scoreEl = scoreEl;
        this.canvas = canvas;
        this.ctx = canvas.getContext("2d");
        this.ripples = [];
        this.nextRippleID = 0;
    }

    shouldReset() {
        return keyboard['KeyR'];
    }

    newRippleID() {
        let id = this.nextRippleID;
        this.nextRippleID++;
        return id;
    }

    // newRipple initializes and stores a new ripple at the given coordinates, as
    // well as all sub-ripples which make up the initial ripple's reflections.
    newRipple(x, y, bounces, color) {
        color = color ? color : palette[Math.floor(Math.random() * palette.length)];

        let ripplePos = [];
        let nextRipples = [];

        let addRipple = (x, y) => {
            for (let i in ripplePos) {
                if (ripplePos[i][0] == x && ripplePos[i][1] == y) return;
            }

            let ripple = new Ripple(this.newRippleID(), this.currTick, x, y, bounces, color);
            nextRipples.push(ripple);
            ripplePos.push([x, y]);
            this.ripples.push(ripple);
        };

        // add initial ripple, after this we deal with the sub-ripples.
        addRipple(x, y);

        while (bounces > 0) {
            bounces--;
            let prevRipples = nextRipples;
            nextRipples = [];

            for (let i in prevRipples) {
                let prevX = prevRipples[i].x;
                let prevY = prevRipples[i].y;
                addRipple(prevX, -prevY);
                addRipple(-prevX, prevY);
                addRipple((2*this.canvas.width)-prevX, prevY);
                addRipple(prevX, (2*this.canvas.height)-prevY);
            }
        }
    }

    // playerRipplesState returns a mapping of rippleID -> boolean, where each
    // boolean indicates the ripple's relation to the player at the moment. true
    // indicates the player is outside the ripple, false indicates the player is
    // within the ripple.
    playerRipplesState() {
        let state = {};
        for (let i in this.ripples) {
            let ripple = this.ripples[i];
            let rippleRadius = ripple.radius(this.currTick);
            let hs = Math.pow(ripple.x-this.player.x, 2) + Math.pow(ripple.y-this.player.y, 2);
            state[ripple.id] = hs > Math.pow(rippleRadius + playerRadius, 2);
        }
        return state;
    }

    playerHasJumpedOverRipple(prev, curr) {
        for (const rippleID in prev) {
            if (!curr.hasOwnProperty(rippleID)) continue;
            if (curr[rippleID] != prev[rippleID]) return true;
        }
        return false;
    }

    update() {
        if (this.state != 'play') return;

        let playerPrevZ = this.player.z;
        this.player.act();

        if (playerPrevZ == 0 && this.player.z > 0) {
            // player has jumped
            this.prevPlayerRipplesState = this.playerRipplesState();

        } else if (playerPrevZ > 0 && this.player.z == 0) {

            // player has landed, don't produce a ripple unless there are no
            // existing ripples or the player jumped over an existing one.
            if (
                this.ripples.length == 0 ||
                this.playerHasJumpedOverRipple(
                    this.prevPlayerRipplesState,
                    this.playerRipplesState()
                )
            ) {
                let bounces = Math.floor((this.player.lastJumpHeight*1.8)+1);
                console.log("spawning ripple with bounces:", bounces);
                this.newRipple(this.player.x, this.player.y, bounces);
                this.score += bounces;
            }
        }

        if (this.player.z == 0) {
            for (let i in this.ripples) {
                let ripple = this.ripples[i];
                let rippleRadius = ripple.radius(this.currTick);
                if (rippleRadius < playerRadius * 1.5) continue;
                let hs = Math.pow(ripple.x-this.player.x, 2) + Math.pow(ripple.y-this.player.y, 2);
                if (hs > Math.pow(rippleRadius + playerRadius, 2)) {
                    continue;
                } else if (hs <= Math.pow(rippleRadius - playerRadius, 2)) {
                    continue;
                } else {
                    console.log("game over", ripple);
                    ripple.winner = true;
                    this.player.loser = true;
                    this.state = 'gameOver';
                    // deliberately don't break here, in case multiple ripples hit
                    // the player on the same frame
                }
            }
        }

        this.ripples = this.ripples.filter(ripple => !ripple.canGC(this.currTick));

        this.currTick++;
    }

    draw() {
        this.ctx.clearRect(0, 0, this.canvas.width, this.canvas.height);
        this.ripples.forEach(ripple => ripple.draw(this.ctx, this.currTick));
        this.player.draw(this.ctx)
        this.scoreEl.innerHTML = this.score;
    }
}


const requestAnimationFrame =
    window.requestAnimationFrame ||
    window.mozRequestAnimationFrame ||
    window.webkitRequestAnimationFrame ||
    window.msRequestAnimationFrame;

let game = new Game(canvas, document.getElementById("score"));

function reset() {
    game = new Game(canvas, document.getElementById("score"));
}

function nextFrame() {
    if (game.shouldReset()) reset();

    game.update()
    game.draw()
    requestAnimationFrame(nextFrame);
}
requestAnimationFrame(nextFrame);

canvas.focus();

</script>

## Changelog

There's been two major changes to the mechanics of the game since the previous
version:

* A new ripple is created _only_ if there are no ripples on the field already,
  or if the player has jumped over an existing ripple.

* The score is increased only if a ripple is created, and is increased by the
  number of bounces off the wall that ripple will have. Put another way, the
  score is increased based on how high you jump.

Other small changes include:

* Ripple growth rate has been modified. It's now harder for a player to run into
  the ripple they just created.

* Ripple thickness indicates how many bounces are left in the ripple. This was
  the case previously, but it's been made more obvious.

* Small performance improvements.