Free
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Rating summary
About
A secret cipher of four colored keys is hidden inside the system. You have seven attempts to crack it.
DECODER is a code-breaking puzzle — a modern take on the classic Mastermind — wrapped in the aesthetic of a green-on-black decryption terminal. Lock in a guess, hit RUN, and the system reports back:
• HIT — right color, right slot
• NEAR — right color, wrong slot
The hints never tell you WHICH slot is right. Read them, reason it out, and narrow the cipher down before your attempts run out. Crack it in four hits to breach the system. Burn all seven and the cipher stays sealed.
NO LUCK. JUST LOGIC.
Every cipher is solvable by pure deduction. There are no power-ups, no timers, no ads, no accounts — just you against the code.
TWO CLEARANCE LEVELS
• EASY · 6 colors — learn the ropes
• ADVANCED · 8 colors — for hardened operators
Colors can repeat, so don't assume the obvious.
BUILT FOR THE CRAFT
• A tactile CRT terminal interface — scanlines, glow, and a blinking cursor
• Colorblind-friendly: every key carries a letter, never color alone
• Honors Reduce Motion
• Tracks your stats per clearance level: solve rate, current streak, and best run
• Fully offline. No sign-up, no tracking, no nonsense.
Read the hints. Breach the system.
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What's New in Decoder Terminal
1.0.1
June 15, 2026
Performance and stability improvements.





