Zaxxon

Zaxxon is the game that introduced isometric scrolling to arcades. You fly a ship diagonally over a scrolling space fortress, and the 3/4 perspective changes everything about how a shooter reads: altitude is a real dimension, judged by the ship's shadow on the ground, and the walls, missiles and barriers all demand height control that no top-down or side-view shooter had asked for.

The shadow is the game's teaching device - watch where you would land and you can thread the fortress's barriers. Fuel tanks line the route and shooting them keeps your gauge alive, running dry costs a life, and the mid-level and end bosses are a confrontational radar dish that fires homing shots along the diagonal axis. Sega released it in 1982 and it was a genuine hit on both sides of the Pacific; the perspective was so distinctive that clone-avoidance terms like 'Zaxxon-view' entered the vocabulary of the era's games press. It is still the reference point for the trick every later isometric shooter had to answer.

• ▸The first major isometric scrolling shooter - altitude via shadow reading
• ▸Fuel gauge economy: shoot tanks or lose a ship
• ▸A homing-shot radar dish boss at the fortress core
• ▸Fortress walls and barriers that demand real height management