What you're looking at here is Super Chain Crusher, a shmup (shoot-em-up) whose native resolution of 3200 x 800 is so long most modern video hardware cannot properly display it.
So its developers encourage you to play it across two screens.
OK, so you technically can play it on one screen - and you can do it right now, as there's a playable demo - but you'd be missing the point, and you wouldn't be playing the game as nature intended.
Here's the breathlessly fantastic description, as laid down by Japanese developers Mindware:
3200 x 800 Adrenaline ! Blow away all standards with shooting on a galactic scale !
WILL WORK WITH ONE MONITOR! TWO IS BEST BUT NOT NEEDED!
A PC game with a stunning 3200x800 pixels for ultra widescreen shooting! Create the longest series of chained explosions ever seen on this massive screen! Completely fill your gigantic ultra charge shot gauge to unleash a massive explosion 2000 pixels wide! It blows away all standards and crushes the competition! Introducing Super Chain Crusher Horizon!
[via Hardcore Gaming]