This is a cross between the currently-hot infinite runner genre and the old-school arcade classic Missile Command.   The theme is directly inspired/stolen directly from the Steve Jackson Games classic Ogre – soon to be re-released in the biggest board game box ever.

You control the Mega Death Tank, a massive and nearly unstoppable killing machine that’s on a suicide mission towards the enemy capital.  The enemy is going to throw everything they’ve got to stop you.  You can’t be killed directly by enemy fire, but as your armor is degraded you become more and more vulnerable to the nuclear radiation on the battlefield.

Your tank will move along on its own.  Occasionally, you might have the option to adjust course, to choose which enemy battle group to fight next or something.   The player needs to use the available weapon systems to deal with the various threats on the map.  The Mega Death Tank has several different guns – several batteries that fire tactical nuclear rounds (maybe with different sizes and ranges) and some short-range lasers, I figure.  Each weapon has a cooldown time.  The player taps a weapon, and then taps a point on the map to shoot.   Main batteries have a bit of travel time, and explode with a large radius of damage – like Missile Command.  The blast area also becomes radioactive – I suppose a color effect of some sort can show this.

Enemy tanks and whatnot have different speeds, different fire ranges, and different toughness.  Some might be killable even if they are just winged by a blast, others might only be stunned, and some might be vulnerable to radiation.  The player may be able to block the approach of some enemies using radiation as a wall – by the time the enemy units drive around, the player will have moved on. The toughest enemy tanks would be slow, but only directly killable if they’re first hit by a laser.  Stunning them for a bit might be enough to leave them in the dust, if you hit them at the right moment.

Driving into a lake might allow for repair, or radiation reduction.

This could be played with timed missions, or on infinite survival mode.   I also have an idea for a slight variation – define a travel path on a real world map, set real-world speeds to everything, and determine the mission time accordingly.  For example, your tank drives up out of the ocean in Normandy, and must drive to Paris.

Expansion DLC could have different Mega Death Tanks, different enemy units, and different maps.

This would work great as an Ogre licensed product, but could also be done independently – I’m imagining a series of battles featuring thoroughly odd sets of real-world opponents, each of which would have their own unique Mega Death Tanks, and their own distinctive mix of defending units.  India vs. Russia!  USA vs Brazil!  Japan vs. France!