Click in front of the moving ball to place a block. The ball will turn 90 degrees at the block depending on the ball’s colour. The computer-controlled paddle at the bottom can change the ball’s colour if the ball hits it. You can also click on an existing block to remove it. – [Author’s statement]
Gridball Inverse (Leon Arnott)
Posted by Porpentine
on May 13, 2012

This is neat, but the current implementation allows for an unfortunate strategy: without any restrictions on block placement, the player can simply block off all four sides of the screen completely, removing any possibility of losing the ball and even removing the bottom paddle from play. After that there’s not really any game left.
Lots of possibilities for fixing this, I imagine. First two to come to mind: make blocks disappear after a few seconds and/or limit the number of active blocks allowed on screen etc.