If you don't know about Halo: Spartan Assault by now, this should give you some insight as to what the game will be like. It's a game exclusive to Microsoft Windows 8 Phone and Windows 8 software (Surface, PCs, etc.).
This is clearly some kind of alien forest like title of the picture states. But you can see here a Spartan using a Needler to kill a Grunt. Notice the view you're looking at the game from.
This is a great image to me. I love how they brought Wolverines back into Halo since Halo Wars. Also notice that there are subtitles going on in the game and health bars for vehicles.
This is a great scene because you have one Spartan bringing up the rear while his partner is crouching around the boxes with a Rocket Launcher. Notice that there is a crouch feature in this game.
You're trying to fight your way across a bridge in this one and you and your partner have taken a Shade Turret to fight their Shade Turret and Wraith.
Ok it turns out that there are tons more screenshots than I thought so I'm going to skip around to some more important shots. Here's the armory, as you can see. Loadouts are featured in this game as well.
Keyboard & Mouse Controls
Here are the keyboard and mouse controls for a PC using Windows 8 software.
Tablet Touch Controls
Here are the touch controls for a Microsoft Surface or Windows 8 Phone like the Nokia Lumia.
Heavy Armor Combat
Tank beats Ghost. Tank beats Hunter. Tank beats everything!
I hope this gives you a better idea of the game before rushing and getting it. There are a lot of cool features but ultimately it's your choice on whether you wanna buy a new phone or computer for it.