diff --git a/common/src/main/scala/net/psforever/packet/game/HotSpotUpdateMessage.scala b/common/src/main/scala/net/psforever/packet/game/HotSpotUpdateMessage.scala
index 9309f3ab7..f3dc760dd 100644
--- a/common/src/main/scala/net/psforever/packet/game/HotSpotUpdateMessage.scala
+++ b/common/src/main/scala/net/psforever/packet/game/HotSpotUpdateMessage.scala
@@ -6,25 +6,43 @@ import scodec.Codec
 import scodec.codecs._
 
 /**
-  * na
-  * @param unk na
+  * Information for positioning a hotspot on the continental map.<br>
+  * <br>
+  * The coordinate values and the scaling value have different endianness than most numbers transmitted as packet data.
+  * The two unknown values are not part of the positioning system, at least not a part of the coordinates.<br>
+  * <br>
+  * The origin point is the lowest left corner of the map grid.
+  * On either axis, the other edge of the map is found at the maximum value 4096 (`FFF`).
+  * The scale is typically set as 128 (`80000`) but can also be made smaller or made absurdly big.
+  * @param unk1 na
   * @param x the x-coord of the center of the hotspot
+  * @param unk2 na
   * @param y the y-coord of the center of the hotspot
-  * @param scale the scaling of the hotspot graphic
+  * @param scale the scaling of the hotspot icon
   */
-final case class HotSpotInfo(unk : Int,
+final case class HotSpotInfo(unk1 : Int,
                              x : Int,
+                             unk2 : Int,
                              y : Int,
                              scale : Int)
 
 /**
-  * na
+  * A list of data for creating hotspots on a continental map.<br>
+  * <br>
+  * The hotspot system is a forgetful all-or-nothing affair.
+  * The packet that is always initially sent during server login clears any would-be hotspots from the map.
+  * Each time a hotspot packet is received for a zone, all of the previous hotspots for that zone are forgotten.
+  * To simply add a hotspot, the next packet has to contain information that re-explains the packets that were originally rendered.<br>
+  * <br>
+  * Exploration 1:<br>
+  * The unknown parameter has been observed with various non-zero values such as 1, 2, and 5.
+  * Visually, however, `unk` does not affect anything.
+  * Does it do something internally?
   * @param continent_guid the zone (continent)
   * @param unk na
-  * @param spots a list of HotSpotInfo, or Nil if empty
+  * @param spots a List of HotSpotInfo, or `Nil` if empty
   */
-// TODO test for size > 0 (e.g., > hex'00')
-// TODO test for size > 15 (e.g., > hex'F0')
+// TODO need aligned/padded list support
 final case class HotSpotUpdateMessage(continent_guid : PlanetSideGUID,
                                       unk : Int,
                                       spots : List[HotSpotInfo] = Nil)
@@ -36,15 +54,16 @@ final case class HotSpotUpdateMessage(continent_guid : PlanetSideGUID,
 
 object HotSpotUpdateMessage extends Marshallable[HotSpotUpdateMessage] {
   implicit val hotspot_codec : Codec[HotSpotInfo] = {
-    ("unk" | uint8L) ::
-      ("x" | uint16L) ::
-      ("y" | uint16L) ::
-      ("scale" | uintL(20))
+    ("unk1" | uint8) ::
+      ("x" | uint(12)) ::
+      ("unk2" | uint8) ::
+      ("y" | uint(12)) ::
+      ("scale" | uint(20))
   }.as[HotSpotInfo]
 
   implicit val codec : Codec[HotSpotUpdateMessage] = (
     ("continent_guid" | PlanetSideGUID.codec) ::
-      ("unk" | uint8L) ::
+      ("unk" | uint4L) ::
       ("spots" | listOfN(uint8L, hotspot_codec))
     ).as[HotSpotUpdateMessage]
 }
diff --git a/common/src/test/scala/GamePacketTest.scala b/common/src/test/scala/GamePacketTest.scala
index 0f88abdfe..288c42cfe 100644
--- a/common/src/test/scala/GamePacketTest.scala
+++ b/common/src/test/scala/GamePacketTest.scala
@@ -916,13 +916,14 @@ class GamePacketTest extends Specification {
     }
 
     "HotSpotUpdateMessage" should {
-      val stringClear = hex"9F 0500 10 00"
+      val stringClear = hex"9F 0500 1 00 0"
+      val stringOne = hex"9F 0500 1 01 0 00 2E9 00 145 80000 0"
 
       "decode (clear)" in {
         PacketCoding.DecodePacket(stringClear).require match {
           case HotSpotUpdateMessage(continent_guid, unk, spots) =>
             continent_guid mustEqual PlanetSideGUID(5)
-            unk mustEqual 16
+            unk mustEqual 1
             spots.size mustEqual 0
           case _ =>
             ko
@@ -930,7 +931,7 @@ class GamePacketTest extends Specification {
       }
 
       "encode (clear)" in {
-        val msg = HotSpotUpdateMessage(PlanetSideGUID(5),16)
+        val msg = HotSpotUpdateMessage(PlanetSideGUID(5),1)
         val pkt = PacketCoding.EncodePacket(msg).require.toByteVector
         pkt mustEqual stringClear
       }