Used by the routine at NEW_GAME.

Called by the main loop every turn (NEW_GAME). When the bonus record is empty it picks a cell: the knight's own column or the one four to its right (the random number's bits 0-2 masked with $FC leave only 0 or 4), and a row from four above his to three below. If that cell is not solid (types 1 and 2) and is not within one cell of the knight, the bonus goes there, at a random place in the middle half of the cell, as graphic 2 or 3 by whether the turn count is even or odd.

So a bonus is almost always about: the moment one is taken, or left behind by more than three cells (SPEED_BONUS), the next turn tries again. One placed four columns to the right is outside the three cells SPEED_BONUS keeps it within, so it goes again on its first update, unless the knight has moved towards it; so does one placed four rows up. Measured in the simulator with the knight standing in cell (16,16): of 330 placements only those in his own column two or three rows away outlasted their first update, and a bonus was there in every one of 300 turns left alone.

The column is wrapped to the town's 32 but the row is looked up before it is wrapped, so a knight in the top four or bottom three rows has the bonus's cell looked up outside the map (PLACE_IN_CELL, from offset 41, adds the row times 32 to the map's address as it is); only the stored row is wrapped.