Hold the bottom of the screen and shoot down flocks of diving birds, and when you can't dodge, throw up a force-field to weather the swoop.
Birds wheel and dive in formation from above. Move along the bottom, shoot them out of the sky, and raise your shield when a swoop is about to hit you. Clear each wave to advance and survive the escalating flocks.
Plume draws on Phoenix, released by Amstar in 1980, which is usually named as one of the first games to end a stage with a single large enemy rather than another wave — the ancestor of the boss fight.
Before that it does something subtler. The large birds can be shot apart piece by piece: take the wings off and the bird is crippled but still coming, worth less and harder to predict. The mothership at the end sits behind a shield you must chew a hole through while it advances, and your only defence is a shield of your own that freezes you in place while it holds.
Plume is an original free browser arcade shooter in the fixed-position blaster tradition, with a defensive shield twist. No install required.