Where Time Stood Still

01 · The calendar

Bug: the calendar shows May twice

Play starts on MAY 1. After 31 May the calendar turns to MAY 1 again, and only then to June, July and August.

The page turn is bank 0's $F465, written again here and held to the game's own code by test_calendar.js. In ZEsarUX, from the start of play with the day set to 31 and the clock to just before midnight, the panel turned to MAY 1 and the month byte $8D15 was 0.

The calendar keeps the day of the month at $8D14 and the month at $8D15, and its names are MAY, JUN, JUL and AUG for months 0 to 3 ($F57E). At midnight the day goes up, and after the month's last day it goes back to 1 and the month to one more, kept to 0 to 3 ($F465). New game sets the month to $FF ($865E), and the panel starts with MAY drawn on it. So the first month is May, and the month after it is $FF plus one, which is month 0: May again.

The month byte has a second job. Bank 3's altar ceremony counts in the same byte: a capture sets it to 0 ($FEB0), the altar counts it up to the sacrifice at $E8 ($FEC8), and the end of a ceremony sets it back to $FF ($FF7F). The altar counts only while the byte is not $FF, and the calendar shows whatever month the count happens to make.

Two things follow. A ceremony that ends puts the calendar back to the start of its cycle, so the next month is May. A month's end with no ceremony running leaves the byte at 0 to 3, and the altar's routine then runs as if a ceremony had started, with character 0, Jarret, as the captive, because the byte that names the captive is 0 from new game ($8D0C). That second consequence is traced in the code and has not been seen in play.

02 · The tribe's speech

Secret: Dirk translates the tribe, whose letters come out mirrored

When a tribesman speaks, every letter of his message is swapped for another, A for Z and B for Y. When Dirk is near enough to hear, the same message follows from him in plain words, beginning HE SAID.

Each letter and what the conversation window prints in its place for a tribesman. The swap is two instructions at bank 3 $D84C: the letter's code taken from $2C. Dirk's translation is queued by $FD95.

The game's small font numbers its letters from $0A for A to $17 for N, then $18 for P to $22 for Z. There is no O: the game prints the digit 0 for it. Taking each code from $2C mirrors the alphabet for most letters, but the missing O moves the middle. M stays M, L and N swap, and O, printed as the digit 0, becomes code $2C, which is past the alphabet. What the font draws for that code was not checked.

The manual only hints at this: Dirk's "studies on obscure eastern dialects may come in useful".

03 · Two areas

Bug: areas 12 and 15 take their scenery from the ROM

The plateau is sixteen areas, four by four, and areas 12 and 15 are the two bottom corners. The game holds no scenery for either of them.

Bank 7's table at $DB00 gives each area's scenery record. Areas 0 and 1 share one, area 8's lies in main memory at $6859, and the words for areas 12 and 15 are $0005 and $3501, inside the ROM.

Loading an area reads its record for the boxes the creatures walk round and the 2 KB of its map ($8A9B), so in either corner the loader would build the map out of whatever the ROM holds at those addresses. Whether a player can reach areas 12 or 15 is an open question: walking off the south edge of areas 8 or 11, or the west edge of 13 and the east edge of 14, would load them (bank 3 $DB0B). The Maps tab leaves them blank.

04 · Unused input

Secret: a fifth joystick that no option offers

The control selection screen offers four ways to play. The code has a fifth input routine, for a joystick on port $7F.

The routine is at $B622, the same shape as the four that are offered: up, down, left and right in bits 0 to 3 of the port, and fire in bit 7.

The title's four options lead to the four other routines, and nothing leads to this one. A player with a joystick on that port has no way to choose it.

05 · An unused reset

Secret: holding CAPS SHIFT would reset the machine

A routine at $BEE0 resets the machine when CAPS SHIFT is held. Nothing calls it.

The routine sets the stack to $5B00 and jumps to address 0 when CAPS SHIFT is down. It sits just before the game's clock ($BEEF), and no instruction in the code maps calls or jumps to it.

Since nothing reaches the routine, holding CAPS SHIFT in play does nothing.

06 · A test that always passes

Bug: the seizing creatures' sound check compares the wrong number

The creatures that seize a victim make a sound on alternate frames: effect $0F for one group, and effect 5 every fourth pass for the other. A check meant to keep effect 5 to a range of creatures compares a constant instead.

Bank 3 $F150: the actor's byte is compared with $9C, and A is loaded with $0F before the jump that uses the comparison. The next comparison, with $A0, then compares that $0F, so it always finds it lower and never skips the sound.

The effect is small: every creature that reaches the second test makes effect 5, whatever its byte, where the code meant to stop at $A0. Effect 5 is also Clive's cry for HELP, and it is on the How it works tab's list of effects.