Used by the routine at WON.

For the game-over screen (WON). Two rooms seen count one per cent, up to 54 (108 rooms or more); each quest item the bucket has reached counts 4 (QUEST_DONE, four of them: 16); each collectable in its place in room 82 counts 6 (PLACED, five: 30). 54, 16 and 30 make 100. The sum is counted up in BCD into PERCENT -- the hundreds, 0 or 1, then the tens and units -- and printed at pixel row 95, column 144 of the buffer: three digits at 100, otherwise two, with a leading zero.

The count is a DJNZ loop, so a sum of 0 runs it 256 times and prints 56: measured in the simulator, a player who loses all five lives without leaving the room he started in is told 56 per cent. One room seen counts nothing, since the rooms are halved first, and two count 1.