Contagion: A Color Flood Strategy Game That’s Deceptively Addictive
Ever stared at a grid of colors and thought, “I can dominate this”?That’s exactly the feeling Contagion delivers — a minimalist strategy game where every color you pick reshapes the battlefield.
What is Contagion?
Contagion is a turn-based territory control game played on an 8×8 grid. Each cell is painted one of six colors. You start from one corner, an AI opponent starts from the opposite corner, and the goal is simple: own more cells than your opponent when the board is full.
On each turn, you pick a color. Every cell touching your territory that matches that color gets absorbed — your empire grows. Then the AI does the same. Back and forth until every cell on the board belongs to someone.
Simple rules. Surprising depth.
How It Works
The game starts with a randomly generated grid — 64 cells, 6 colors, infinite possibilities. Your territory begins as a single cell in the top-left corner. The AI claims the bottom-right.
When you tap a color from the palette at the bottom of the screen:
- All cells in your territory change to that color
- Any adjacent cells already matching that color get absorbed into your territory
- This cascades outward — a chain reaction of conquest
The trick? You’re not just picking the color that grabs the most cells right now. You’re thinking two, three moves ahead. That cluster of yellow in the middle looks tempting, but grabbing those two blue cells first might open a path to a massive purple region on the next turn.
The AI Doesn’t Go Easy
The AI opponent uses a greedy strategy — it evaluates every possible color choice and picks whichever one captures the most cells. It’s not playing randomly. It’s calculating.
This means you can’t win by just tapping colors mindlessly. You need to:
- Block the AI’s expansion paths by claiming key bridge cells
- Think about color distribution — which colors appear most near your border?
- Sacrifice small gains for big ones — sometimes taking 1 cell now sets up taking 8 next turn
Why It’s Addictive
Contagion hits that sweet spot between “I understand this immediately” and “I need to play one more round.” Games last about 2 minutes. The board is different every time. And there’s always that nagging feeling that you could’ve played better.
The visual feedback is satisfying too — watching your color flood across the grid, cells flipping to your side in a cascade. And then watching the AI do the same from the other corner, creeping toward your territory.
It’s a quiet kind of tension. No timers. No reflexes needed. Just you, the AI, and a grid full of colored cells waiting to be claimed.
The Design Philosophy
We wanted Contagion to feel like a board game on your phone. Dark background, vibrant cell colors, clean typography. No flashy animations or distracting particles. Just the grid, the palette, and the score.
The six colors — red, blue, green, yellow, purple, and orange — were chosen for maximum visual distinction. You should never confuse one for another, even at a glance. The player’s cells get a subtle brightness boost while the AI’s cells appear slightly muted, so you can always read the board state instantly.
Strategy Tips
Opening moves matter. Look at the colors surrounding your starting corner. Pick the color that appears most in your immediate neighborhood — early territory gains compound quickly.
Watch the center. The middle of the board is contested ground. Whoever reaches it first often wins because central cells connect to more neighbors in every direction.
Don’t always pick the greedy move. The AI picks the maximum-capture color every single turn. You can beat it by thinking longer-term — setting up positions that the greedy algorithm can’t see coming.
Color scarcity wins games. If there are only three purple cells on the board and they’re all near your border, grabbing them removes that color as a useful option for the AI.
Built With
- Flutter — cross-platform, smooth 60fps rendering
- Zero dependencies — pure Flutter SDK, no external packages
- ChangeNotifier pattern — clean reactive state management
- BFS flood fill — the core algorithm that makes territory expansion work
Try It
Contagion is the kind of game you open for “just one round” and look up 30 minutes later wondering where the time went. The rules fit in a sentence. The strategy keeps you coming back.
Pick a color. Spread your territory. Dominate the grid.