javascript making a tag game

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30 Mar 2017

1 <!-- A SIMPLE SNAKE GAME MADE BY HTML AND CSS -->
2
3<!DOCTYPE html>
4<html>
5<head>
6  <title></title>
7  <style>
8  html, body {
9    height: 100%;
10    margin: 0;
11  }
12
13  body {
14    background: black;
15    display: flex;
16    align-items: center;
17    justify-content: center;
18  }
19  canvas {
20    border: 1px solid white;
21  }
22  </style>
23</head>
24<body>
25<canvas width="400" height="400" id="game"></canvas>
26<script>
27var canvas = document.getElementById('game');
28var context = canvas.getContext('2d');
29
30var grid = 16;
31var count = 0;
32  
33var snake = {
34  x: 160,
35  y: 160,
36  
37  // snake velocity. moves one grid length every frame in either the x or y direction
38  dx: grid,
39  dy: 0,
40  
41  // keep track of all grids the snake body occupies
42  cells: [],
43  
44  // length of the snake. grows when eating an apple
45  maxCells: 4
46};
47var apple = {
48  x: 320,
49  y: 320
50};
51
52// get random whole numbers in a specific range
53// @see https://stackoverflow.com/a/1527820/2124254
54function getRandomInt(min, max) {
55  return Math.floor(Math.random() * (max - min)) + min;
56}
57
58// game loop
59function loop() {
60  requestAnimationFrame(loop);
61
62  // slow game loop to 15 fps instead of 60 (60/15 = 4)
63  if (++count < 4) {
64    return;
65  }
66
67  count = 0;
68  context.clearRect(0,0,canvas.width,canvas.height);
69
70  // move snake by it's velocity
71  snake.x += snake.dx;
72  snake.y += snake.dy;
73
74  // wrap snake position horizontally on edge of screen
75  if (snake.x < 0) {
76    snake.x = canvas.width - grid;
77  }
78  else if (snake.x >= canvas.width) {
79    snake.x = 0;
80  }
81  
82  // wrap snake position vertically on edge of screen
83  if (snake.y < 0) {
84    snake.y = canvas.height - grid;
85  }
86  else if (snake.y >= canvas.height) {
87    snake.y = 0;
88  }
89
90  // keep track of where snake has been. front of the array is always the head
91  snake.cells.unshift({x: snake.x, y: snake.y});
92
93  // remove cells as we move away from them
94  if (snake.cells.length > snake.maxCells) {
95    snake.cells.pop();
96  }
97
98  // draw apple
99  context.fillStyle = 'red';
100  context.fillRect(apple.x, apple.y, grid-1, grid-1);
101
102  // draw snake one cell at a time
103  context.fillStyle = 'green';
104  snake.cells.forEach(function(cell, index) {
105    
106    // drawing 1 px smaller than the grid creates a grid effect in the snake body so you can see how long it is
107    context.fillRect(cell.x, cell.y, grid-1, grid-1);  
108
109    // snake ate apple
110    if (cell.x === apple.x && cell.y === apple.y) {
111      snake.maxCells++;
112
113      // canvas is 400x400 which is 25x25 grids 
114      apple.x = getRandomInt(0, 25) * grid;
115      apple.y = getRandomInt(0, 25) * grid;
116    }
117
118    // check collision with all cells after this one (modified bubble sort)
119    for (var i = index + 1; i < snake.cells.length; i++) {
120      
121      // snake occupies same space as a body part. reset game
122      if (cell.x === snake.cells[i].x && cell.y === snake.cells[i].y) {
123        snake.x = 160;
124        snake.y = 160;
125        snake.cells = [];
126        snake.maxCells = 4;
127        snake.dx = grid;
128        snake.dy = 0;
129
130        apple.x = getRandomInt(0, 25) * grid;
131        apple.y = getRandomInt(0, 25) * grid;
132      }
133    }
134  });
135}
136
137// listen to keyboard events to move the snake
138document.addEventListener('keydown', function(e) {
139  // prevent snake from backtracking on itself by checking that it's 
140  // not already moving on the same axis (pressing left while moving
141  // left won't do anything, and pressing right while moving left
142  // shouldn't let you collide with your own body)
143  
144  // left arrow key
145  if (e.which === 37 && snake.dx === 0) {
146    snake.dx = -grid;
147    snake.dy = 0;
148  }
149  // up arrow key
150  else if (e.which === 38 && snake.dy === 0) {
151    snake.dy = -grid;
152    snake.dx = 0;
153  }
154  // right arrow key
155  else if (e.which === 39 && snake.dx === 0) {
156    snake.dx = grid;
157    snake.dy = 0;
158  }
159  // down arrow key
160  else if (e.which === 40 && snake.dy === 0) {
161    snake.dy = grid;
162    snake.dx = 0;
163  }
164});
165
166// start the game
167requestAnimationFrame(loop);
168</script>
169</body>
170</html>

Calvin

11 Feb 2016

1//Javascript game template
2//Move player with arrow keys
3
4var canvas = document.createElement("canvas");
5canvas.width = 500;
6canvas.height = 500;
7document.body.appendChild(canvas);
8var ctx = canvas.getContext("2d");
9
10var player = {x: canvas.width / 2, y: canvas.height / 2, speed: 10};
11var keys = [];
12
13function update() {
14  ctx.clearRect(0, 0, canvas.width, canvas.height);
15  
16  ctx.beginPath();
17  ctx.fillStyle = "red";
18  ctx.fillRect(player.x, player.y, 50, 50);
19  
20  if (keys[37])
21    player.x -= player.speed;
22  if (keys[38])
23    player.y -= player.speed;
24  if (keys[39])
25    player.x += player.speed;
26  if (keys[40])
27    player.y += player.speed;
28  
29  requestAnimationFrame(update);
30}
31update();
32
33document.onkeydown = function(e) {
34  keys[e.keyCode] = true;
35}
36document.onkeyup = function(e) {
37  keys[e.keyCode] = false;
38}

Silvia

02 May 2020

1(function)game=tag
2(function)=character=109
3(function)=vehicles=200

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