OXO

Three in a row. Then do it again before the board buries you.

OXO is a falling block puzzler for the Game Boy Color. X's and O's drop into a six by twelve well. Line up three or more of the same mark in any direction, across, down, or either diagonal, and they clear. If the pieces that fall into the gap line up too, the chain multiplier climbs and the next clear is worth more.

That's the whole rule set. Everything else is the board making it harder.

The board fights back

Four things show up in the drop queue that aren't X's or O's, and each one changes the shape of the problem.

• Blockers are inert cyan cells. They never match. The only way to remove one is to clear a match right next to it.
• Trapped pieces are an X or an O sealed inside a shell. They won't match while trapped, so land a piece on top to break one open.
• Jokers count as both X and O at once, and resolve into whichever run they help most. They're the cheapest way to start a chain.
• Garbage rows shove up from the bottom when you go too long without clearing anything. The stack doesn't wait for you.

Gravity ramps with the number of pieces you've placed. A run that felt comfortable at three hundred tiles will not at eight hundred.

Chains

The multiplier runs from x1 to x3 across five chain steps, and the five segment bar in the CHAIN card shows exactly how deep you are. Clears also pay bonuses for every blocker broken, every trapped piece freed, every garbage cell removed, and for any joker that took part. A well aimed joker into a blocker cluster is worth several plain matches.

The scoring rewards patience over speed. Soft dropping into a setup you've already built beats hard dropping into a fresh one.

Controls

On a Game Boy:

• D-pad left and right move the falling piece
• Down soft drops
• Up, A or B hard drops
• A or B confirms on the menu and the game over screen

On PC, the bundled player maps the same buttons to your keyboard:

• Arrow keys for the D-pad
• X for A, Z for B
• Enter for Start, Backspace or Right Shift for Select
• Alt+Enter toggles fullscreen, Escape leaves it

Any controller works too, on the standard gamepad layout.

What you get

Buying OXO gets you both ways to play it:

• OXO.gbc, the raw ROM. It runs on original hardware from a flashcart, and on any accurate emulator. The cartridge is MBC5 with battery backed save RAM, so your high score survives the power switch.
• Desktop players for Windows, Linux and macOS, each with the GB# Player built in. Nothing to install and nothing to configure, just the game in its own window.

A Steam key is included once OXO is live on Steam.

Built in C#

OXO is written in C# and compiled to a native Game Boy Color ROM with GBSharp. Every visual on this page comes out of the same asset generator that produces the ROM's graphics, so what you see here is what runs on the hardware.