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2

DOOM comes from an era when stability of the game's rules/mechanics actually mattered. Folks were generally unhappy when an upgrade to the game broke their existing demo recordings, and for the most part, the updates to the game engine avoided doing that. Note that this also matters for things like trying to score achievements, where changes to the rules, ...


-1

This seems to be just neglectful programming. The other answers mention Doom (and Doom II) being based on a ‘2½-dimensional’ engine (later retroactively named id Tech 1), meaning the engine internally keeps floor and ceiling heights bolted on to what would otherwise be a two-dimensional map. While this is true, and it does limit the game environment in ...


0

Think in the other direction: Monsters chase players, if they are allowed to be above a player, they are in a spot where they cannot be seen and cannot be shot at.


41

Doom maps and locations on the maps were essentially 2D. This makes a lot of stuff much cheaper to calculate that a general 3D solution but has some limitations: objects can't stack, you can't jump over them, you can shoot them by aiming over/under them and paths can't pass over/under other paths. But 99% of the time you don't notice any of this :o)


31

Allowing two objects to occupy the same position in XY space but different elevations would create the possibility that one object might collide with another from above or below. While this might not be a problem when dealing with projectile weapons that would naturally be destroyed in the collision, it would pose some complications if e.g. a player could ...


9

This might be Home Planet, developed by John Walker. The second release was published as freeware in 1994, and ran on Windows 3.1. (I haven't been able to track down information about the previous version.) Its main screen (which is also usable as a screensaver) shows the day and night areas of the earth's surface, albeit without time zones: (screenshot ...


18

The one I know is GeoClock, though it looks like its website is no longer in operation. It can still be found in Simtel archives, along with extra maps. You can also see an older version in action on the Internet Archive.


4

It probably wasn't this: Amateur Radio Clock. But this type of clock application is popular with ham radio operators. What you're describing sounds a lot like a software version of a Geochron. These are mechanical maps of the world with light and dark bands that move across the projected planet.


10

The 16-color modes on the VGA use a hardware design borrowed from the EGA. On the EGA (and VGA), the bitwise drawing modes don't act upon memory directly, but instead act upon values stored in four eight-bit registers, each of which holds a byte of data from one of four color planes. Reading any byte of data from the display will load each of the four ...


14

Running your code as-is on a real 286/VGA (Cirrus Logic CL-GD5420) produces this image: Inserting one dummy read before the second fill cycle (just mov ax, es:[0]) gives the image you were expecting: So it would seem that at least there might be a difference between the DOSBox implementation and the real hardware. If it does implement logic operations, ...


7

Since it is a Commodore PC 30-III, the mouse port is not a serial port and no serial mice should be plugged into it. The mouse port is only compatible with Commodore mice that send the quadrature signals directly, i.e. so called bus mice. If you want to plug in a serial mouse, you must use the only serial port with the DB-25 connector.


3

In the age of serial mice, there were two completely incompatible standards that most mice emulated (many had a physical switch to select either of both, eg the popular Genius brand mice) - "Microsoft" and "Mouse Systems". A 3 button mouse without a switch is very likely "Mouse Systems" and needs a driver compatible with that ...


0

Port 023C sounds like it could be compatible with a Microsoft InPort bus mouse. Try a MS mouse driver for DOS (version 8.20 or older) with parameter /I1 or /I2.


20

Since your mouse has three buttons, it won’t use the same protocol as Microsoft mice (at least, in three-button mode), and won’t be fully supported by the Microsoft driver. Presumably the mouse was originally provided with a suitable driver; if you can find that, it should work. Alternatively, you can try CuteMouse, which is a DOS mouse driver with support ...


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