-
Notifications
You must be signed in to change notification settings - Fork 0
/
Basic Helicopter Game
234 lines (202 loc) · 6.21 KB
/
Basic Helicopter Game
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
<!DOCTYPE html>
<html>
<head>
<title>Basic Helicopter HTML Game</title>
<meta charset="UTF-8">
<style>
html, body {
height: 100%;
margin: 0;
}
body {
background: black;
display: flex;
align-items: center;
justify-content: center;
}
</style>
</head>
<body>
<canvas width="800" height="550" id="game"></canvas>
<script>
const canvas = document.getElementById('game');
const context = canvas.getContext('2d');
const minTunnelWidth = 400;
const maxTunnelWidth = canvas.width;
const minHeight = 10;
const maxHeight = 100;
const obstacleWidth = 65;
const obstacleHeight = 135;
// how fast the background moves
const moveSpeed = 7;
// downward acceleration
const gravity = 0.35;
// keep track of the spacebar being pressed so we can move the
// helicopter up when pressed and down when not pressed
let spacePressed = false;
// clamp a number between min and max values
function clamp(num, min, max) {
return Math.min( Math.max(min, num), max);
}
// return a random integer between min (inclusive) and max (inclusive)
// @see https://stackoverflow.com/a/1527820/2124254
function randInt(min, max) {
return Math.floor(Math.random() * (max - min + 1)) + min;
}
const helicopter = {
x: 200,
y: 100,
width: 100,
height: 60,
dy: 0, // velocity
ddy: 0 // acceleration
};
// just keep track of a tunnel wall current x position, width, start
// and end height. the top and bottom wall are mirrored, so we only
// need to keep track of one of them
let tunnels = [{
x: 0,
width: canvas.width,
start: 50,
end: 50
},
{
x: canvas.width,
width: randInt(minTunnelWidth, maxTunnelWidth),
start: 50,
end: randInt(minHeight, maxHeight)
}];
// for the obstacles in the path just need to keep track of the
// position as they are always the same size
let obstacles = [{
x: canvas.width,
y: canvas.height / 2
},
{
x: canvas.width * 2,
y: canvas.height / 2
}];
// tunnel wall color and rgb value
const wallColor = 'green';
context.fillStyle = wallColor;
context.fillRect(0, 0, 1, 1);
// getImageData returns a data object which is a flat array of every
// pixel of the canvas in the specified rect (x, y, width, height).
// every 4 indices of the array is a single pixel's r,g,b,a values
const wallData = context.getImageData(0, 0, 1, 1);
// destructure the image data array to get the rgb values of the wall
// @see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Destructuring_assignment
const [ wallRed, wallGreen, wallBlue ] = wallData.data;
// game loop
let rAF;
function loop() {
rAF = requestAnimationFrame(loop);
context.clearRect(0,0,canvas.width,canvas.height);
if (spacePressed) {
helicopter.ddy = -0.7;
}
else {
helicopter.ddy = 0;
}
// update position based on acceleration and velocity
helicopter.dy += helicopter.ddy + gravity;
// clamp velocity
helicopter.dy = clamp(helicopter.dy, -8, 8);
helicopter.y += helicopter.dy;
// draw the helicopter
context.fillStyle = 'white';
context.fillRect(helicopter.x, helicopter.y, helicopter.width, helicopter.height);
// draw the tunnel walls over the helicopter
context.fillStyle = 'green';
tunnels.forEach((tunnel, index) => {
tunnel.x -= moveSpeed;
// if the last tunnel is fully on screen, we need to spawn a new
// tunnel segment off screen
if (
index === tunnels.length - 1 &&
tunnel.x + tunnel.width <= canvas.width
) {
tunnels.push({
x: tunnel.x + tunnel.width,
width: randInt(minTunnelWidth, maxTunnelWidth),
start: tunnel.end,
end: randInt(minHeight, maxHeight)
});
}
// top tunnel wall
context.beginPath();
context.moveTo(tunnel.x, 0);
context.lineTo(tunnel.x, tunnel.start);
context.lineTo(tunnel.x + tunnel.width, tunnel.end);
context.lineTo(tunnel.x + tunnel.width, 0);
context.closePath();
context.fill();
// bottom tunnel wall
context.beginPath();
context.moveTo(tunnel.x, canvas.height);
context.lineTo(tunnel.x, tunnel.start + 450);
context.lineTo(tunnel.x + tunnel.width, tunnel.end + 450);
context.lineTo(tunnel.x + tunnel.width, canvas.height);
context.closePath();
context.fill();
});
// draw obstacles
obstacles.forEach((obstacle, index) => {
obstacle.x -= moveSpeed;
context.fillRect(obstacle.x, obstacle.y, obstacleWidth, obstacleHeight);
// if the last obstacle is fully on screen, we need to spawn a new
// one off screen
if (
index === obstacles.length - 1 &&
obstacle.x + obstacleWidth <= canvas.width
) {
obstacles.push({
x: canvas.width * 2,
y: randInt(maxHeight + 50, canvas.height - obstacleHeight - maxHeight - 50)
});
}
});
// remove any tunnel segments or obstacles that are off screen
tunnels = tunnels.filter(tunnel => tunnel.x + tunnel.width > 0);
obstacles = obstacles.filter(obstacle => obstacle.x + obstacleWidth > 0);
// pixel perfect collision detection
// get the pixels of the canvas at the helicopter rect and look for
// any pixels that match the wall color. the wall has to be drawn
// above the helicopter in order for this to work
const { data } = context.getImageData(helicopter.x, helicopter.y, helicopter.width, helicopter.height);
for (let i = 0; i < data.length; i += 4) {
const r = data[i];
const g = data[i + 1];
const b = data[i + 2];
// if we match the tunnel wall color we have a collision
if (r === wallRed && g === wallGreen && b === wallBlue) {
// draw a dotted red circle around the helicopter when it
// crashes
context.strokeStyle = 'red';
context.setLineDash([5, 15])
context.lineWidth = 4;
context.beginPath();
context.arc(helicopter.x + helicopter.width / 2, helicopter.y + helicopter.height / 2, helicopter.width, 0, 2 * Math.PI);
context.stroke();
cancelAnimationFrame(rAF);
}
}
}
// listen to keyboard events to move the helicopter
document.addEventListener('keydown', function(e) {
// spacebar
if (e.code === 'Space') {
spacePressed = true;
}
});
document.addEventListener('keyup', function(e) {
// spacebar
if (e.code === 'Space') {
spacePressed = false;
}
});
// start the game
rAF = requestAnimationFrame(loop);
</script>
</body>
</html>