curriculum/challenges/english/blocks/learn-intermediate-oop-by-building-a-platformer-game/65afeb7ab6867b43dacbf32b.md
As you are designing the game, you will need to make sure that the size of the elements in the game are responsive and adapt to different screen sizes.
Start by creating an arrow function called proportionalSize that takes in a size parameter.
proportionalSize should be a function.
assert.isFunction(proportionalSize);
Your proportionalSize function should use arrow syntax.
assert.match(code, /const\s+proportionalSize\s*=\s*\(?\s*.*\s*\)?\s*=>/);
Your proportionalSize function should have a size parameter.
assert.match(code, /const\s+proportionalSize\s*=\s*\(?\s*size\s*\)?\s*=>/);
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>Learn Intermediate OOP by Building a Platformer Game</title>
<link rel="stylesheet" href="./styles.css" />
</head>
<body>
<div class="start-screen">
<h1 class="main-title">freeCodeCamp Code Warrior</h1>
<p class="instructions">
Help the main player navigate to the yellow checkpoints.
</p>
<p class="instructions">
Use the keyboard arrows to move the player around.
</p>
<p class="instructions">You can also use the spacebar to jump.</p>
<div class="btn-container">
<button class="btn" id="start-btn">Start Game</button>
</div>
</div>
<div class="checkpoint-screen">
<h2>Congrats!</h2>
<p>You reached the last checkpoint.</p>
</div>
<canvas id="canvas"></canvas>
<script src="./script.js"></script>
</body>
</html>
* {
margin: 0;
padding: 0;
box-sizing: border-box;
}
:root {
--main-bg-color: #0a0a23;
--section-bg-color: #ffffff;
--golden-yellow: #feac32;
}
body {
background-color: var(--main-bg-color);
}
.start-screen {
background-color: var(--section-bg-color);
width: 100%;
position: absolute;
top: 50%;
left: 50%;
margin-right: -50%;
transform: translate(-50%, -50%);
border-radius: 30px;
padding: 20px;
padding-bottom: 5px;
}
.main-title {
text-align: center;
}
.instructions {
text-align: center;
font-size: 1.2rem;
margin: 15px;
line-height: 2rem;
}
.btn {
cursor: pointer;
width: 100px;
margin: 10px;
color: #0a0a23;
font-size: 18px;
background-color: var(--golden-yellow);
background-image: linear-gradient(#fecc4c, #ffac33);
border-color: var(--golden-yellow);
border-width: 3px;
}
.btn:hover {
background-image: linear-gradient(#ffcc4c, #f89808);
}
.btn-container {
display: flex;
align-items: center;
justify-content: center;
}
.checkpoint-screen {
position: absolute;
left: 0;
right: 0;
margin-left: auto;
margin-right: auto;
width: 100%;
text-align: center;
background-color: var(--section-bg-color);
border-radius: 20px;
padding: 10px;
display: none;
}
#canvas {
display: none;
}
@media (min-width: 768px) {
.start-screen {
width: 60%;
max-width: 700px;
}
.checkpoint-screen {
max-width: 300px;
}
}
const startBtn = document.getElementById("start-btn");
const canvas = document.getElementById("canvas");
const startScreen = document.querySelector(".start-screen");
const checkpointScreen = document.querySelector(".checkpoint-screen");
const checkpointMessage = document.querySelector(".checkpoint-screen > p");
const ctx = canvas.getContext("2d");
canvas.width = innerWidth;
canvas.height = innerHeight;
const gravity = 0.5;
let isCheckpointCollisionDetectionActive = true;
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