The Last Ace

The Last Ace is another one to chalk up to nostalgia. It's a side-scrolling shmup with 16-color pixellated graphics -- early arcade, or perhaps NES-level. Four lives, no additional ones ever, no continue. Your score depends partly on killing enemies (of which there are a variety, with different attack patterns), and partly on survival -- you earn 5 points/second for being in the lower half of the screen (which is generally modestly safer), and 10 points if in the upper half.

Gameplay is somewhat Gradius-like, without the boss battles -- multiple levels and waves of attackers, a difficulty level that ramps up over time. Nothing fancy, but not a bad little time-waster, in a retro way.