Beast

Beast (1984), created by Dan Baker, is an absolute masterpiece of early character-based DOS gaming. It is a brilliant, highly addictive block-pushing tactical puzzle game that proved you didn't need fancy graphics to create an incredibly intense gameplay experience.Instead of sprites, the entire game is rendered using standard ASCII text characters in DOS text mode.
You control a little character represented by a blue diamond symbol (or sometimes a smiley face depending on the character set). You are trapped on a single-screen grid with several "Beasts" (usually represented by a capital H). The Beasts are faster than you, and if they touch you, you die instantly. You have no weapons, no guns, and no magic. The only way to survive and clear the level is to crush the Beasts by pushing green blocks into them, or trapping them so tightly that they have no moves left and explode.
The game relies entirely on aggressive AI pathfinding and clever geometry:
The AI Aggression: The Beasts (the H characters) possess a simple but relentless AI—they always calculate the shortest diagonal or straight path directly toward your current coordinates.
Pushable Blocks: The screen is filled with green blocks. You can push a single block (or a whole row of them) if there is empty space behind them. If a Beast is right on the other side of a block and you push it forward, you crush it.
Static Obstacles: There are also yellow, immovable blocks scattered around. You have to use these to create "bottlenecks" to trap the moving enemies.
The Proximity Multiplier: As you progress to higher levels, the game introduces tougher variants of the monsters (like "Super Beasts") that move even faster or can break through regular blocks if you don't act quickly.

What is abandonware ?