Zanac

Zanac is a vertical shooter from Compile, and it is remembered for something almost no other 1986 game attempted: the game watches how you are playing and changes the difficulty to match.

That system is the whole reason to play it. Blitz through a stage with a high weapon level and the game will throw denser waves and more aggressive enemies at you; struggle, and it eases off. It is an early, deliberate attempt at dynamic difficulty, and it means a skilled run is genuinely harder than a bad one rather than just faster. On top of that the weapon system swaps between eight numbered fire modes as you collect power-ups, so you are choosing between spread, homing and direct fire rather than just stacking damage. It began on the MSX before the Famicom conversion, and Compile went on to build Aleste and the rest of its shooter line on the same foundations.

• ▸Adaptive difficulty that responds to how well the player is doing
• ▸Eight numbered weapon modes swapped with collected power-ups
• ▸Dense scripted enemy patterns built for repeat runs
• ▸Two firing buttons, so both thumbs are used at once