Havoc is a decent facsimile of Zaxxon. The object is to reach a base before it gets destroyed, avoiding various perils on the way.
The screen shows a stylistic 'urban' scene - blocks of green, grey roads with white dashes down the middle, and a backdrop made of big monolithic structures with blue open spaces between them. You're shown as a delta-winged fighter and below is your shadow, which changes as you bank left and right via joystick control. But I found the 'forward to dive, backwards to climb' combination hard to get used to at first.
Once you've taken off, and begin to glide serenely about, you come across the first hazard - enemy fighters. These aren't portrayed very well, and look like WWII V1 rockets. Surprisingly the fighters don't fire at you or chase you - but they can be tricky to avoid and difficult to shoot down, especially if you've moved up to the right of the screen.
With regards to the other hazards, keep an eye on your shadow to help you get your bearings. Once past these you're up against a hail of gargantuan black bombs which descend at a rate of knots, their mission to make a pizza of your plane.
If you want to know how well you're doing, dive down and taxi, your wing-tips flash and the screen display clears to a 'Statrep' (Status Report) which shows how much damage has been done to your craft and the base you're trying to reach.
Should you dodge the bomb phase, a wall blocks further movement. At the base there's a narrow aperture and manoeuvring through this without losing those useful wings is no picnic.
Through the hole lies a similar screen, but obviously it's a lot harder.
The graphics are good and clear and the scrolling impressive.
However, the action's a bit limited and the left/right joystick response was sometimes a little sticky. Even so, it's not an easy game and certainly worth a look.