Simple HTML Platformer

To create a simple HTML platformer, you can follow these steps:

1. Create a new HTML file and name it something like 'platformer.html'.
2. Inside the HTML file, create a canvas element where you will draw the game. For example:

<canvas id='gameCanvas' width='800' height='600'></canvas>

3. Create a JavaScript file named 'platformer.js' and link it to your HTML file using the script tag. Make sure to link it after the canvas element so that you can reference it in the JavaScript code. For example:

<script src='platformer.js'></script>

4. In the JavaScript file, create a function called drawGame that will draw the game on the canvas. For example:

function drawGame() {
  var canvas = document.getElementById('gameCanvas');
  var ctx = canvas.getContext('2d');
  
  // Draw the game here
}

5. Inside the drawGame function, you can draw the player, platforms, and any other game elements you want using the ctx context. For example:

function drawGame() {
  var canvas = document.getElementById('gameCanvas');
  var ctx = canvas.getContext('2d');
  
  // Draw the player
  ctx.fillStyle = 'red';
  ctx.fillRect(50, 50, 50, 50);
  
  // Draw the platforms
  ctx.fillStyle = 'green';
  ctx.fillRect(0, 550, 800, 50);
  ctx.fillRect(300, 400, 200, 50);
  
  // Draw any other game elements
}

6. Add keyboard controls to move the player left and right. You can use the addEventListener function to listen for key presses and move the player accordingly. For example:

document.addEventListener('keydown', function(event) {
  if(event.key === 'ArrowLeft') {
    // Move the player left
  }
  else if(event.key === 'ArrowRight') {
    // Move the player right
  }
});

7. Add gravity to make the player fall down when not on a platform. You can update the player's position every frame and detect collisions with the platforms to determine if the player is on the ground or not. For example:

var player = {
  x: 50,
  y: 50,
  width: 50,
  height: 50,
  velocityX: 0,
  velocityY: 0,
  onGround: false
};

function updatePlayer() {
  // Apply gravity
  player.velocityY += 0.5;
  
  // Move the player
  player.x += player.velocityX;
  player.y += player.velocityY;
  
  // Check for collisions with platforms
  if(player.y + player.height > 550) {
    player.y = 550 - player.height;
    player.velocityY = 0;
    player.onGround = true;
  }
  else if(player.y + player.height > 400 && player.x + player.width > 300 && player.x < 500) {
    player.y = 400 - player.height;
    player.velocityY = 0;
    player.onGround = true;
  }
  else {
    player.onGround = false;
  }
}

8. Finally, call the drawGame and updatePlayer functions every frame using the requestAnimationFrame function. For example:

function gameLoop() {
  drawGame();
  updatePlayer();
  requestAnimationFrame(gameLoop);
}

gameLoop();

This is just a basic example of how to create a simple HTML platformer. You can add more game elements, levels, and features to make it more complex and challenging. Good luck!