Negative values
Posted: Fri Mar 30, 2007 6:26 pm
I don't know if this has been discovered before, but I'll post it anyway.
I've been fooling around with the ZZT file format for about the last week or so. There are two numeric types used - unsigned 8-bit integers and signed 16-bit integers (little endian). Basically, that means that the numbers ZZT uses either fall in the range of 0 to 255, or -32,768 to 32767.
I find this interesting, because a lot of the numbers in ZZT don't make sense if they're negative. There are such things as 16-bit unsigned integers (range of 0 to 65535), but for some reason, the only 16-bit integers ZZT uses are signed.
So, I started wondering what would happen if you inserted negative values where they didn't belong. As it turns out, you get some pretty interesting stuff!
Unfortunately, none of it is really useful. Items and cheats can modify negative counters, but #give and #take can't. Some counters don't do anything interesting (I was kind of hoping negative health would make some kind of unkillable zombie, but it just ends the game). There are a couple of internal counters that indicate how much of a lit torch or activated energizer is left. Negative values for these don't do anything useful. You can set them to 32,767 to start off the game with a lit torch and an activated energizer that remain for a really long time (almost an hour if I'm calculating right), but once it burns out, it's out, and all other energizers/torches should last for the default duration.
If you set ammo to -1, you can still shoot, and your ammo count keeps on going down (-2, -3, etc...). After 32,767 shots, the counter is at -32,768. This is the lowest possible number - another shot will cause it to wrap around to 32,767, the highest possible number (think odometers here). This means you get a total of 65,535 shots before your ammo count reaches zero. This does not work for torches, though.
However, this doesn't really matter for practical game making. To get near-infinite ammo and torches, a #give ammo 10000 and a #give torches 10000 at the beginning of the game is good enough for almost all purposes, and in my opinion, it's more elegant to avoid negative numbers. Negative values in ZZT are really more of a curiosity than anything else.
I've been fooling around with the ZZT file format for about the last week or so. There are two numeric types used - unsigned 8-bit integers and signed 16-bit integers (little endian). Basically, that means that the numbers ZZT uses either fall in the range of 0 to 255, or -32,768 to 32767.
I find this interesting, because a lot of the numbers in ZZT don't make sense if they're negative. There are such things as 16-bit unsigned integers (range of 0 to 65535), but for some reason, the only 16-bit integers ZZT uses are signed.
So, I started wondering what would happen if you inserted negative values where they didn't belong. As it turns out, you get some pretty interesting stuff!
Unfortunately, none of it is really useful. Items and cheats can modify negative counters, but #give and #take can't. Some counters don't do anything interesting (I was kind of hoping negative health would make some kind of unkillable zombie, but it just ends the game). There are a couple of internal counters that indicate how much of a lit torch or activated energizer is left. Negative values for these don't do anything useful. You can set them to 32,767 to start off the game with a lit torch and an activated energizer that remain for a really long time (almost an hour if I'm calculating right), but once it burns out, it's out, and all other energizers/torches should last for the default duration.
If you set ammo to -1, you can still shoot, and your ammo count keeps on going down (-2, -3, etc...). After 32,767 shots, the counter is at -32,768. This is the lowest possible number - another shot will cause it to wrap around to 32,767, the highest possible number (think odometers here). This means you get a total of 65,535 shots before your ammo count reaches zero. This does not work for torches, though.
However, this doesn't really matter for practical game making. To get near-infinite ammo and torches, a #give ammo 10000 and a #give torches 10000 at the beginning of the game is good enough for almost all purposes, and in my opinion, it's more elegant to avoid negative numbers. Negative values in ZZT are really more of a curiosity than anything else.