Sure! I've created a simple game based on your description using JavaScript. Since it needs to be implemented as a single HTML file, I'll provide the entire code below the bear can move
To play the game on a smartphone or desktop browser, simply copy the above code and save it as an HTML file (e.g., "game.html"). Open the file in your preferred browser, and you should be able to control the red circle (the lost kid) using the arrow keys. The green circles (bears) will move randomly towards the bottom right corner, and if any bear collides with the kid, you'll see a "Game Over!" alert.