This is the arcade classic in a browser build of the kind Google has featured in its own games and doodles: five rows of invaders descending in formation, four shields to hide behind, and a laser cannon that can only have one shot in the air at a time.
The 1978 original by Tomohiro Nishikado is where the shooting-game genre really began, and its most famous quirk is preserved here — the aliens speed up as you destroy them, because the original hardware could redraw fewer sprites faster. What began as a hardware limitation became the defining feature.
The 1978 arcade hardware could only draw so many sprites per frame, so with fewer aliens left the game simply ran faster. Players loved the escalating tension, so every version since has kept it deliberately.
Google has featured arcade-style games in its doodles and Search Playground over the years. This page runs a faithful browser version of the classic so you can play it any time.
Yes — a tiny 2D game with two controls and nothing to install.