diff --git a/MarathonData.md b/MarathonData.md
index 0b04d82..c720edc 100644
--- a/MarathonData.md
+++ b/MarathonData.md
@@ -446,8 +446,8 @@ is 6.9s, but the integral part is ignored. "No angle" is represented by 65510
 The type "`unit`" refers to a 16-bit fixed point number with the format 5.10s.
 This is used for all world coordinates.
 
-An "Optional Short" is a 16-bit integer which references something by index. If
-all bits are set, it is to be interpreted as "none." Traditionally, these are
+A "`u16opt`" is a 16-bit integer which references something by index. If all
+bits are set, it is to be interpreted as "none." Traditionally, these are
 signed integers, but they can be treated as unsigned with no repercussions.
 
 ## Wad ##
@@ -578,9 +578,9 @@ Side Texture is 6 bytes. Just stores a texture and an offset.
 | ----           | ----       | ------ |
 | `OffsetX`      | `unit`     | `0`    |
 | `OffsetY`      | `unit`     | `2`    |
-| `TextureId`    | `u16`      | `4`    |
+| `TextureId`    | `u16opt`   | `4`    |
 
-- `TextureId` is an Optional Short referencing a Shapes bitmap.
+- `TextureId` references a Shapes bitmap.
 
 ### Point ###
 
@@ -622,19 +622,17 @@ Line is 32 bytes. A geometric line segment.
 | `Length`       | `unit`     | `6`    |
 | `HeightHi`     | `unit`     | `8`    |
 | `HeightLo`     | `unit`     | `10`   |
-| `SideFrnt`     | `u16`      | `12`   |
-| `SideBack`     | `u16`      | `14`   |
-| `PolyFrnt`     | `u16`      | `16`   |
-| `PolyBack`     | `u16`      | `18`   |
+| `SideFrnt`     | `u16opt`   | `12`   |
+| `SideBack`     | `u16opt`   | `14`   |
+| `PolyFrnt`     | `u16opt`   | `16`   |
+| `PolyBack`     | `u16opt`   | `18`   |
 
 - `PointBeg` and `PointEnd` are the beginning and terminating endpoints.
 - `Flags` is a Line Flags bit field.
 - `HeightHi` and `HeightLo` are the highest adjacent ceiling and lowest
 adjacent floor heights, respectively.
-- `SideFrnt` and `SideBack` are Optional Short indices of the Sides in the
-front and back.
-- `PolyFrnt` and `PolyBack` are Optional Short indices of the connected
-Polygons.
+- `SideFrnt` and `SideBack` are indices of the Sides in the front and back.
+- `PolyFrnt` and `PolyBack` are indices of the connected Polygons.
 
 ### Side ###
 
@@ -706,11 +704,11 @@ shape and automatically split them.)
 | `SideArray`    | `u16[8]`   | `92`   |
 | `OrigFlr`      | `struct`   | `108`  |
 | `OrigCei`      | `struct`   | `112`  |
-| `Media`        | `u16`      | `116`  |
+| `Media`        | `u16opt`   | `116`  |
 | `MediaLight`   | `u16`      | `118`  |
 | `SoundIndices` | `u16`      | `120`  |
-| `SoundAmbient` | `u16`      | `122`  |
-| `SoundRandom`  | `u16`      | `124`  |
+| `SoundAmbient` | `u16opt`   | `122`  |
+| `SoundRandom`  | `u16opt`   | `124`  |
 
 - `Type` is a Polygon Type enumeration.
 - `Flags` is a Polygon Flags bit field.
@@ -719,9 +717,6 @@ shape and automatically split them.)
 - `Center` is a Point structure.
 - `OrigFlr` is a Point structure for the texture offset of the floor.
 - `OrigCei` is a Point structure for the texture offset of the ceiling.
-- `Media` is an Optional Short.
-- `SoundAmbient` is an Optional Short.
-- `SoundRandom` is an Optional Short.
 
 ### Light ###
 
@@ -847,14 +842,13 @@ part of the map in the middle of a wall.
 | `Origin`       | `struct`   | `14`   |
 | `Height`       | `unit`     | `18`   |
 | `Minimum`      | `fixed`    | `20`   |
-| `Texture`      | `u16`      | `24`   |
+| `Texture`      | `u16opt`   | `24`   |
 | `XferMode`     | `u16`      | `26`   |
 
 - `Type` is a Media Type enumeration.
 - `Flags` is a Media Flags bit field.
 - `Control` is the index of a light which is used to control the height of this
 media.
-- `Texture` is an Optional Short representing the texture index.
 - `XferMode` is a Transfer Mode enumeration.
 
 ### Static Map Info ###
@@ -1190,7 +1184,7 @@ Frame is 36 bytes. TODO: document how world transform works.
 | ----           | ----       | ------ |
 | `Flags`        | `u16`      | `0`    |
 | `MinLight`     | `fixed`    | `2`    |
-| `BmpIndex`     | `u16`      | `6`    |
+| `BmpIndex`     | `u16opt`   | `6`    |
 | `WldLeft`      | `unit`     | `14`   |
 | `WldRight`     | `unit`     | `16`   |
 | `WldTop`       | `unit`     | `18`   |
@@ -1200,7 +1194,6 @@ Frame is 36 bytes. TODO: document how world transform works.
 
 - `Flags` is a Frame Flags bit field.
 - `MinLight` is the minimum light intensity (0-1.)
-- `BmpIndex` is an Optional Short for the bitmap index.
 
 ### Sequence ###
 
@@ -1291,7 +1284,7 @@ Sound Definition is 64 bytes.
 
 | Name           | Type       | Offset |
 | ----           | ----       | ------ |
-| `Code`         | `u16`      | `0`    |
+| `Code`         | `u16opt`   | `0`    |
 | `Volume`       | `u16`      | `2`    |
 | `Flags`        | `u16`      | `4`    |
 | `Chance`       | `u16`      | `6`    |
@@ -1303,7 +1296,6 @@ Sound Definition is 64 bytes.
 | `GroupSize`    | `u32`      | `28`   |
 | `AddOffset`    | `u32[5]`   | `32`   |
 
-- `Code` is an Optional Short referencing something (TODO.)
 - `Volume` is a Sound Behaviour enumeration.
 - `Flags` is a Sound Definition Flags bit field.
 - `Chance` is the chance out of `65535` that the sound will not play.
diff --git a/src/durandal/bin.rs b/src/durandal/bin.rs
index b0a98f8..5a5a857 100644
--- a/src/durandal/bin.rs
+++ b/src/durandal/bin.rs
@@ -39,9 +39,9 @@ macro_rules! rd_1 {
       rd_1!($b u16::from_be_bytes, $nam 2 $n);
       let $nam = Unit::from_bits($nam);
    };
-   (BE $b:ident $nam:ident OptShort $n:expr) => {
+   (BE $b:ident $nam:ident OptU16 $n:expr) => {
       rd_1!($b u16::from_be_bytes, $nam 2 $n);
-      let $nam = OptShort::from_repr($nam);
+      let $nam = OptU16::from_repr($nam);
    };
 
    // little endian
@@ -154,19 +154,19 @@ pub fn rd_ofstable<T, F>(b: &[u8],
    Ok(v)
 }
 
-impl OptShort
+impl OptU16
 {
-   /// Creates an `OptShort` from a `u16`.
-   pub fn from_repr(n: u16) -> OptShort
+   /// Creates an `OptU16` from a `u16`.
+   pub fn from_repr(n: u16) -> OptU16
    {
       if n == u16::max_value() {
-         OptShort(None)
+         OptU16(None)
       } else {
-         OptShort(NonZeroU16::new(n + 1))
+         OptU16(NonZeroU16::new(n + 1))
       }
    }
 
-   /// Returns the `u16` representation of an `OptShort`.
+   /// Returns the `u16` representation of an `OptU16`.
    pub fn get_repr(&self) -> u16
    {
       match self.0 {
@@ -175,7 +175,7 @@ impl OptShort
       }
    }
 
-   /// Returns the `Option` representation of an `OptShort`.
+   /// Returns the `Option` representation of an `OptU16`.
    pub fn get(&self) -> Option<u16>
    {
       match self.0 {
@@ -185,7 +185,7 @@ impl OptShort
    }
 }
 
-impl fmt::Debug for OptShort
+impl fmt::Debug for OptU16
 {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result
    {
@@ -202,6 +202,6 @@ pub type Ident = [u8; 4];
 /// An object identified by a `u16` which may be `u16::max_value()` to
 /// represent None.
 #[derive(Serialize)]
-pub struct OptShort(Option<NonZeroU16>);
+pub struct OptU16(Option<NonZeroU16>);
 
 // EOF
diff --git a/src/marathon/map.rs b/src/marathon/map.rs
index 8dc4cb4..1347ab1 100644
--- a/src/marathon/map.rs
+++ b/src/marathon/map.rs
@@ -44,7 +44,7 @@ pub fn read_sidetex(b: &[u8]) -> ResultS<SideTex>
    read_data! {
       6, BE in b =>
       offs   = read_point[0..4];
-      tex_id = OptShort[4];
+      tex_id = OptU16[4];
    }
 
    Ok(SideTex{offs, tex_id})
@@ -83,10 +83,10 @@ pub fn read_lins(b: &[u8]) -> ResultS<(Line, usize)>
       pnt_beg = u16[0];
       pnt_end = u16[2];
       flags   = u16[4];
-      side_fr = OptShort[12];
-      side_bk = OptShort[14];
-      poly_fr = OptShort[16];
-      poly_bk = OptShort[18];
+      side_fr = OptU16[12];
+      side_bk = OptU16[14];
+      poly_fr = OptU16[16];
+      poly_bk = OptU16[18];
    }
 
    let flags = flag_ok!(LineFlags, flags)?;
@@ -127,8 +127,8 @@ pub fn read_poly(b: &[u8]) -> ResultS<(Polygon, usize)>
       128, BE in b =>
       ptype   = u16[0];
       pdata   = i16[4];
-      tex_flr = OptShort[40];
-      tex_cei = OptShort[42];
+      tex_flr = OptU16[40];
+      tex_cei = OptU16[42];
       hei_flr = Unit[44];
       hei_cei = Unit[46];
       lit_flr = u16[48];
@@ -137,11 +137,11 @@ pub fn read_poly(b: &[u8]) -> ResultS<(Polygon, usize)>
       xfr_cei = u16[66];
       ori_flr = read_point[108..112];
       ori_cei = read_point[112..116];
-      med_ind = OptShort[116];
+      med_ind = OptU16[116];
       med_ctl = u16[118];
       snd_ind = u16[120];
-      snd_amb = OptShort[122];
-      snd_rnd = OptShort[124];
+      snd_amb = OptU16[122];
+      snd_rnd = OptU16[124];
    }
 
    let xfr_flr = TransferMode::from_repr(xfr_flr)?;
@@ -262,7 +262,7 @@ pub fn read_medi(b: &[u8]) -> ResultS<(Media, usize)>
       orig    = read_point[14..18];
       hei_nrm = Unit[18];
       min_lt  = Fixed[20];
-      texture = OptShort[24];
+      texture = OptU16[24];
       xfer    = u16[26];
    }
 
@@ -304,17 +304,17 @@ pub struct Line
    pub flags:   LineFlags,
    pub pnt_beg: u16,
    pub pnt_end: u16,
-   pub side_fr: OptShort,
-   pub side_bk: OptShort,
-   pub poly_fr: OptShort,
-   pub poly_bk: OptShort,
+   pub side_fr: OptU16,
+   pub side_bk: OptU16,
+   pub poly_fr: OptU16,
+   pub poly_bk: OptU16,
 }
 
 #[derive(Debug, Serialize)]
 pub struct SideTex
 {
    pub offs:   Point,
-   pub tex_id: OptShort,
+   pub tex_id: OptU16,
 }
 
 #[derive(Debug, Serialize)]
@@ -338,8 +338,8 @@ pub struct Polygon
 {
    pub ptype:   PolyType,
    pub pdata:   i16,
-   pub tex_flr: OptShort,
-   pub tex_cei: OptShort,
+   pub tex_flr: OptU16,
+   pub tex_cei: OptU16,
    pub hei_flr: Unit,
    pub hei_cei: Unit,
    pub lit_flr: u16,
@@ -348,11 +348,11 @@ pub struct Polygon
    pub xfr_cei: TransferMode,
    pub ori_flr: Point,
    pub ori_cei: Point,
-   pub med_ind: OptShort,
+   pub med_ind: OptU16,
    pub med_ctl: u16,
    pub snd_ind: u16,
-   pub snd_amb: OptShort,
-   pub snd_rnd: OptShort,
+   pub snd_amb: OptU16,
+   pub snd_rnd: OptU16,
 }
 
 #[derive(Debug, Serialize)]
@@ -440,7 +440,7 @@ pub struct Media
    pub orig:    Point,
    pub hei_nrm: Unit,
    pub min_lt:  Fixed,
-   pub texture: OptShort,
+   pub texture: OptU16,
    pub xfer:    TransferMode,
 }
 
diff --git a/src/marathon/phy.rs b/src/marathon/phy.rs
index 8868cb6..288a6d7 100644
--- a/src/marathon/phy.rs
+++ b/src/marathon/phy.rs
@@ -48,8 +48,8 @@ pub fn read_fxpx(b: &[u8]) -> ResultS<(Effect, usize)>
       shape      = u16[2];
       pitch      = Fixed[4];
       flags      = u16[8];
-      delay      = OptShort[10];
-      delay_snd  = OptShort[12];
+      delay      = OptU16[10];
+      delay_snd  = OptU16[12];
    }
 
    let flags = flag_ok!(EffectFlags, flags)?;
@@ -95,8 +95,8 @@ pub struct Effect
    pub shape:      u16,
    pub pitch:      Fixed,
    pub flags:      EffectFlags,
-   pub delay:      OptShort,
-   pub delay_snd:  OptShort,
+   pub delay:      OptU16,
+   pub delay_snd:  OptU16,
 }
 
 bitflags! {
diff --git a/src/marathon/shp.rs b/src/marathon/shp.rs
index 4834da2..e27247e 100644
--- a/src/marathon/shp.rs
+++ b/src/marathon/shp.rs
@@ -147,9 +147,9 @@ fn sequence(b: &[u8]) -> ResultS<Sequence>
       key     = u16[44];
       xfer    = u16[46];
       xfer_pd = u16[48];
-      snd_beg = OptShort[50];
-      snd_key = OptShort[52];
-      snd_end = OptShort[54];
+      snd_beg = OptU16[50];
+      snd_key = OptU16[52];
+      snd_end = OptU16[54];
       loop_f  = u16[58];
    }
 
@@ -355,9 +355,9 @@ pub struct Sequence
    key:     u16,
    xfer:    TransferMode,
    xfer_pd: u16,
-   snd_beg: OptShort,
-   snd_key: OptShort,
-   snd_end: OptShort,
+   snd_beg: OptU16,
+   snd_key: OptU16,
+   snd_end: OptU16,
    loop_f:  u16,
 }