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Car Racing Game
This recipe demonstrates RxJS implementation of Car Racing game.
Example Code
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Car Racing
index.ts
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// RxJS v6+
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import {
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interval,
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fromEvent,
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combineLatest,
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of,
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BehaviorSubject,
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noop
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} from 'rxjs';
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import {
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scan,
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tap,
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pluck,
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startWith,
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takeWhile,
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finalize,
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switchMap
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} from 'rxjs/operators';
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import { Car, Road, Player, Game } from './interfaces';
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import { gameHeight, gameWidth, levelDuration } from './constants';
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import { updateState } from './state';
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import { render, renderGameOver } from './html-renderer';
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​
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const car = (x: number, y: number): Car => ({ x, y, scored: false });
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const randomCar = (): Car =>
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car(0, Math.floor(Math.random() * Math.floor(gameWidth)));
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const gameSpeed$ = new BehaviorSubject(200);
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​
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const road$ = gameSpeed$.pipe(
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switchMap(i =>
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interval(i).pipe(
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scan(
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(road: Road, _: number): Road => (
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(road.cars = road.cars.filter(c => c.x < gameHeight - 1)),
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road.cars[0].x === gameHeight / 2
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? road.cars.push(randomCar())
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: noop,
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road.cars.forEach(c => c.x++),
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road
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),
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{ cars: [randomCar()] }
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)
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)
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)
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);
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​
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const keys$ = fromEvent(document, 'keyup').pipe(
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startWith({ code: '' }),
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pluck('code')
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);
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​
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const player$ = keys$.pipe(
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scan(
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(player: Player, key: string): Player => (
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(player.y +=
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key === 'ArrowLeft' && player.y > 0
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? -1
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: key === 'ArrowRight' && player.y < gameWidth - 1
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? 1
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: 0),
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player
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),
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{ y: 0 }
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)
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);
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​
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const state$ = of({
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score: 1,
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lives: 3,
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level: 1,
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duration: levelDuration,
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interval: 200
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});
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​
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const isNotGameOver = ([state]: Game) => state.lives > 0;
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​
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const game$ = combineLatest(state$, road$, player$).pipe(
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scan(updateState(gameSpeed$)),
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tap(render),
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takeWhile(isNotGameOver),
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finalize(renderGameOver)
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);
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​
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game$.subscribe();
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state.ts
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import { BehaviorSubject, noop } from 'rxjs';
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import { Game } from './interfaces';
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import { gameHeight, gameWidth, levelDuration } from './constants';
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​
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const handleScoreIncrease = ([state, road, player]: Game) =>
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!road.cars[0].scored &&
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road.cars[0].y !== player.y &&
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road.cars[0].x === gameHeight - 1
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? ((road.cars[0].scored = true), (state.score += 1))
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: noop;
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​
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const handleCollision = ([state, road, player]: Game) =>
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road.cars[0].x === gameHeight - 1 && road.cars[0].y === player.y
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? (state.lives -= 1)
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: noop;
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​
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const updateSpeed = ([state]: Game, gameSpeed: BehaviorSubject<number>) => (
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(state.duration -= 10),
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state.duration < 0
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? ((state.duration = levelDuration * state.level),
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state.level++,
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(state.interval -= state.interval > 60 ? 20 : 0),
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gameSpeed.next(state.interval))
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: () => {}
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);
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​
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export const updateState = (gameSpeed: BehaviorSubject<number>) => (
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_,
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game: Game
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) => (
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handleScoreIncrease(game),
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handleCollision(game),
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updateSpeed(game, gameSpeed),
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game
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);
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html-renderer.ts
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import { Game } from './interfaces';
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import { gameHeight, gameWidth, car, player } from './constants';
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​
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const createElem = (column: number) =>
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(elem => (
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(elem.style.display = 'inline-block'),
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(elem.style.marginLeft = '3px'),
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(elem.style.height = '12px'),
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(elem.style.width = '6px'),
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(elem.style.borderRadius = '40%'),
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(elem.style['background-color'] =
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column === car ? 'green' : column === player ? 'blue' : 'white'),
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elem
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))(document.createElement('div'));
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​
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export const render = ([state, road, playerPosition]: Game) =>
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(renderFrame => (
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road.cars.forEach(c => (renderFrame[c.x][c.y] = car)),
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(document.getElementById(
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'game'
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).innerHTML = `Score: ${state.score} Lives: ${state.lives} Level: ${state.level}`),
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(renderFrame[gameHeight - 1][playerPosition.y] = player),
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renderFrame.forEach(r => {
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const rowContainer = document.createElement('div');
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r.forEach(c => rowContainer.appendChild(createElem(c)));
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document.getElementById('game').appendChild(rowContainer);
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})
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))(
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Array(gameHeight)
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.fill(0)
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.map(e => Array(gameWidth).fill(0))
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);
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​
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export const renderGameOver = () =>
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(document.getElementById('game').innerHTML += '<br/>GAME OVER!!!');
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interfaces.ts
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export interface Car {
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x: number;
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y: number;
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scored: boolean;
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}
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​
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export interface Road {
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cars: Car[];
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}
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​
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export interface State {
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score: number;
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lives: number;
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level: number;
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duration: number;
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interval: number;
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}
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​
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export interface Player {
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y: number;
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}
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​
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export type Game = [State, Road, Player];
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constants.ts
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export const gameHeight = 10;
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export const gameWidth = 6;
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​
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export const levelDuration = 500;
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​
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export const car = 1;
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export const player = 2;
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index.html
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<style>
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.road {
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width: 100px;
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height: 180px;
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margin-top: 25px;
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overflow: hidden;
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position: absolute;
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}
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​
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.dotted {
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margin-top: -100px;
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height: 300px;
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border-left: 2px dashed lightgray;
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position: absolute;
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animation: road-moving 1s infinite linear;
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}
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​
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@keyframes road-moving {
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100% {
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transform: translateY(100px);
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}
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}
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</style>
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​
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<div class="road">
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<div class="dotted" style="margin-left: 0px;"></div>
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<div class="dotted" style="margin-left: 9px;"></div>
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<div class="dotted" style="margin-left: 18px;"></div>
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<div class="dotted" style="margin-left: 27px;"></div>
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<div class="dotted" style="margin-left: 36px;"></div>
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<div class="dotted" style="margin-left: 45px;"></div>
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<div class="dotted" style="margin-left: 54px;"></div>
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</div>
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<div id="game"></div>
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Operators Used
Last modified 1yr ago