Hostile All Terrain Encounter, for any anti-abbreviationists who may be reading, is a diagonally (yes, diagonally) scrolling shoot-'em-up that I seem to remember from my slightly less fortunate Spectrum days.
Each level is in the form of a strip, complete with hills and terrains which you alternate between flying a space ship and driving a tank over. Nothing much has changed from the Spectrum (that, if anything, seemed slightly 'cuter'), but here it's still quite enjoyable and even addictive.
The best feature is the pods - these attach themselves to your vehicle, determining the number of lives you have on the next level (as you don't have to start on level one each time, but instead on the one you died on). The worst thing about it is it was given away free with an old, long-forgotten copy of New Computer Express, but since it's now impossible to get a back copy, why not try it?