I gave myself a 24-hour challenge to come up with a new game that took advantage of Harry Wilhelm's BASIC compiler. I took the basic layout of Crystal Garden and made it into more of a fast-paced puzzle/block-clearing type of game.
In Demolish, you have a limited amount of time to clear as much of the board as possible, by highlighting 3 or more adjacent tiles of the same color, and then demolishing them (causing the tiles above them to shift downward). The more tiles you demolish in one move, the more points each one is worth.
When the timer runs out, you lose one point for each tile still on the board. It's quite possible to end the game with zero points. But if you clear some big groups of tiles out and keep moving, your score will rise quickly.
Use ESDX to move in any of the four cardinal directions (no diagonals are used in Demolish). Hit SPACE to "set your charges" (this turns the tile black). Once you do this, you can only "set charges" on adjacent, same color tiles. If you made a mistake, you can press P and your "charges" will be cleared away without penalty.
Once you've set all your charges, hit C and they'll blow up, and you'll be rewarded points.
Full 22x32 board of tiles
The black tiles on the upper left are where charges have been set. When I hit C, those will blow up and be cleared away.
Time's almost up, and we've cleared a nice bit of the board
A new high score