4Stack #21 — answers & breakdown
Monday, August 3, 2026
Retro games sorted by era, and then one group sorted by publisher instead. Mixing the two axes is the whole puzzle.
The sixteen cards in this puzzle were: Pac-Man, Galaga, Donkey Kong, Space Invaders, Pitfall!, Asteroids, Centipede, Breakout, Sonic the Hedgehog, Street Fighter II, Chrono Trigger, EarthBound, Contra, Castlevania, Gradius, Frogger.
The four stacks
Arcade classics
Pac-Man, Galaga, Donkey Kong, Space Invaders
The arcade canon — the four titles most likely to appear on a stock photo of an arcade.
Atari-era hits
Pitfall!, Asteroids, Centipede, Breakout
The Atari 2600 era, though Pitfall! is an Activision game. Activision was founded by four ex-Atari programmers who wanted credit for their work, which is why it exists at all.
16-bit icons
Sonic the Hedgehog, Street Fighter II, Chrono Trigger, EarthBound
16-bit icons spanning Sega and Nintendo, and two of the most influential RPGs ever made.
Konami classics
Contra, Castlevania, Gradius, Frogger
Konami — and this is where the board fights you. Frogger and Gradius are arcade games that would sit very comfortably in yellow, so you have to notice that a publisher group exists before the era groups will resolve.
Want to try it yourself? Play puzzle #21 — archive plays don't affect your streak. Or jump into today's puzzle.