The game really feels and looks like Halo even though is not a FPS. It has the same atmosphere and the same graphic and artistic direction, making it a real Halo game.
These being said, the game is actually designed for mobile touch enabled devices and the first thing that gives it away is the missions length that never reaches 10 minutes. In fact, you can finish most of the missions in less than 5 minutes(if you're good enough), making Halo: Spartan Assault the first casual game in this series.
The story is interesting and it's written in such a manner that can justify the moments when the game gets really hard.
The game features and experience system that allows you to buy new weapons and abilities. You can get XP points only based on the enemies you kill and the manner you kill them. This way you can earn the Bronze/Silver/Gold star or none (this means no XP points). You can also select 2 out of 6 skulls to make the game harder but gain more XP points.
The game is really enjoyable but unfortunately it has some serious issues.
There are moments the game feels so scripted and cheap that you really want to ditch it.
The default weapons set usually feels useless so you have to pick your own custom ones. However this requires a lot of XP points and force you to pick up skulls. This makes the game harder but frustrating and cheap.
While the Covenant troops have no problem in controlling the vehicles, you struggle to.
While the need 1-3 grenades to blow up their own vehicles when you are driving them, you need 3-5 at least to do the same thing with the same vehicles. While they can blow up you vehicle really fast with mounted turrets without stopping from shooting, you need more shots and time to do it and you also have to stop firing since the turrets magically start overheating when you use them.
And you also need more grenades to blow up the turrets when the enemy uses it than they need for when you are using it.
All those aspects make some missions so hard that you have to keep on trying to finish them. Sometimes you need to replay old missions to get XP points so that you can afford the right set of weapons and abilities since you waste all those points trying to figure the right set out, making a 5 minutes mission feel like a 30 minutes repetitive hell and a very bad way to make a game feel longer than it really is.