У вашего броузера проблема в совместимости с HTML5
Metal Slug Slowdown Fix. Greatly improve the frame rate on all your metal slug games. Metal slug is one of the greatest side scrolling shoot em ups of all time but it has one annoying problem the slow down.
In this video I will show you how to fix the slow frame rate with a cpu overclock
I play Metal Slug on the raspberry pi 3 using retropie and attract mode. If you want to know more about attract mode and retropie check out this video: https://www.youtube.com/watch?v=wI9roQjFihg&t=54s
To get started with retropie and attract mode you will need to get these:
Raspberry pi 3: http://amzn.to/2oNhWzt
Wired Xbox 360 Controller: http://amzn.to/2oF8vW8
Micro SD Card for your image I recommend getting a 128GB card
16GB Sandisk Micro SD: http://amzn.to/2oF8DoA
32GB Sandisk Micro SD: http://amzn.to/2nHUd25
64GB Sandisk Micro SD: http://amzn.to/2oF4GQB
128GB Sandisk Micro SD: http://amzn.to/2oNAoYH
200GB Sandisk Micro SD: http://amzn.to/2oNlXUA