Sierra 7 had a mobile version of it made a while back (just look up "Sierra 7" on either the app store or google play). While still in Early Access, it's also still a fairly good game - a free one, too. If you've played the original flash game, you know what to expect - on-rails shooting with some nice-looking guns.
A few things to take note of:
* If you've played Lonewolf (also by SHD Games), you're likely familiar with the payment model this game has - free players have limited access to weapons and gear, and are also restricted by an energy system. This can be removed by purchasing premium for $4.99, which will also remove ads and give the player eight thousand credits to spend acquiring the newly expanded selection.
* Taking cover, first introduced in the final mission of the flash game, now pops up much more - it's an important way to defend yourself when you're being fired at by multiple opponents.
* Enemies have now evolved considerably from the stickmen from the flash game. These enemies include hostage takers, armored enemies, shielded enemies, and grenadiers (not to mention a few foes I probably haven't run into yet).
* Weapons now work on a "mastery" system - after achieving a certain number of kills, headshots, and hits, guns can be upgraded for improved stats.
* Gear is now a feature! Each piece of gear can influence things like the amount of ammo you'll have available on a mission, how much armor you have, and your "fear rating" (enemies have a chance to be intimidated and not shoot you).
* There is now an actual storyline - Operator 7 returns after a long absence to help take out a militia.
* Medium difficulty can be rather hard if you're not used to twin-stick controls on a mobile device, so don't be discouraged if you die a lot.
All in all, I'd say this is effectively the flash game but made better in several ways.