Flappy Bird Game

By adamlubek

This recipe demonstrates RxJs implementation of Flappy Bird like game.

Ultimate RxJS

Example Code

( StackBlitz )

Flappy Bird

index.ts

// RxJS v6+
import { interval, merge, combineLatest, fromEvent } from 'rxjs';
import { tap, scan, takeWhile } from 'rxjs/operators';
import { paint } from './html-renderer';
const gamePipe = (x, y) => ({ x, y, checked: false });
const gameSize = 10;
const createPipes = y =>
(random =>
Array.from(Array(gameSize).keys())
.map(e => gamePipe(e, y))
.filter(e => e.x < random || e.x > random + 2))(
Math.floor(Math.random() * Math.floor(gameSize))
);
const gamePipes$ = interval(500).pipe(
scan < any,
any >
(acc =>
(acc.length < 2 ? [...acc, createPipes(gameSize)] : acc)
.filter(c => c.some(e => e.y > 0))
.map(cols => cols.map(e => gamePipe(e.x, e.y - 1))),
[createPipes(gameSize / 2), createPipes(gameSize)])
);
const fly = xPos => (xPos > 0 ? (xPos -= 1) : xPos);
const fall = xPos => (xPos < gameSize - 1 ? (xPos += 1) : gameSize - 1);
const bird$ = merge(interval(300), fromEvent(document, 'keydown')).pipe(
scan < any,
any >
((xPos, curr) => (curr instanceof KeyboardEvent ? fly(xPos) : fall(xPos)),
gameSize - 1)
);
const updateGame = (bird, pipes) =>
(game => (
pipes.forEach(col => col.forEach(v => (game[v.x][v.y] = 2))),
(game[bird][0] = 1),
game
))(
Array(gameSize)
.fill(0)
.map(e => Array(gameSize).fill(0))
);
const valueOnCollisionFor = pipes => ({
when: predicate =>
!pipes[0][0].checked && predicate ? ((pipes[0][0].checked = true), 1) : 0
});
combineLatest(bird$, gamePipes$)
.pipe(
scan < any,
any >
((state, [bird, pipes]) => ({
bird: bird,
pipes: pipes,
lives:
state.lives -
valueOnCollisionFor(pipes).when(
pipes.some(c => c.some(c => c.y === 0 && c.x === bird))
),
score:
state.score + valueOnCollisionFor(pipes).when(pipes[0][0].y === 0)
}),
{ lives: 3, score: 0, bird: 0, pipes: [] }),
tap(state =>
paint(updateGame(state.bird, state.pipes), state.lives, state.score)
),
takeWhile(state => state.lives > 0)
)
.subscribe();

html-renderer.ts

const createElem = col => {
const elem = document.createElement('div');
elem.classList.add('board');
elem.style.display = 'inline-block';
elem.style.marginLeft = '10px';
elem.style.height = '6px';
elem.style.width = '6px';
elem.style['background-color'] =
col === 0
? 'white'
: col === 1
? 'cornflowerblue'
: col === 2
? 'gray'
: 'silver';
elem.style['border-radius'] = '90%';
return elem;
};
export const paint = (game: number[][], lives, score) => {
document.body.innerHTML = `Lives: ${lives}, Score: ${score}`;
game.forEach(row => {
const rowContainer = document.createElement('div');
row.forEach(col => rowContainer.appendChild(createElem(col)));
document.body.appendChild(rowContainer);
});
};

Operators Used