refactor: embed TeamArenaState as proper DDGame field

Replace the opaque _unknown_4620 blob with a proper team_arena field
at DDGame+0x4628. The previously separate init_field_64d8 and
init_field_72a4 were actually team_arena.team_count and
team_arena.weapon_slots[754] respectively — now accessed correctly.

fire_skip_go uses ddgame.team_arena._teams_region directly instead
of raw pointer arithmetic through offsets::TEAM_ARENA_STATE.

Verified: headless PASS (byte-identical).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

crates/openwa-core/src/engine/ddgame.rs

@@ -175,19 +175,14 @@ pub struct DDGame {
     /// Initialized to 0x10000 (1.0). Not read by the render method — may be
     /// target/previous value for interpolation, or used by update logic.
     pub team_health_ratio_2: [i32; 6],
-    /// 0x4620-0x64D7: Unknown
-    ///
-    /// Known landmarks:
-    /// - 0x64D8: cleared by init
-    pub _unknown_4620: [u8; 0x64D8 - 0x4620],
-    /// 0x64D8: Cleared by InitFields. Purpose unknown.
-    pub init_field_64d8: u32,
-    /// 0x64DC-0x72A3: Unknown
-    pub _unknown_64dc: [u8; 0x72A4 - 0x64DC],
-    /// 0x72A4: Cleared by InitFields. Purpose unknown.
-    pub init_field_72a4: u32,
-    /// 0x72A8-0x72D7: Unknown
-    pub _unknown_72a8: [u8; 0x72D8 - 0x72A8],
+    /// 0x4620-0x4627: Unknown
+    pub _unknown_4620: [u8; 0x4628 - 0x4620],
+    /// 0x4628: Team arena state — per-team data, ammo, delays, alliance tracking.
+    /// Note: fields previously named init_field_64d8 (= team_count at arena+0x1EB0)
+    /// and init_field_72a4 (= weapon_slots entry at arena+0x2A7C) are inside this struct.
+    pub team_arena: TeamArenaState,
+    /// 0x7270-0x72D7: Unknown
+    pub _unknown_7270: [u8; 0x72D8 - 0x7270],
 
     /// 0x72D8: Game speed multiplier (Fixed-point, 0x10000 = 1.0x).
     pub game_speed: i32,
@@ -415,8 +410,10 @@ pub unsafe fn ddgame_init_fields(ddgame: *mut DDGame) {
         *(base.add(off) as *mut u32) = 0;
     }
 
-    (*ddgame).init_field_64d8 = 0;
-    (*ddgame).init_field_72a4 = 0;
+    // init_field_64d8 = TeamArenaState.team_count (arena+0x1EB0)
+    (*ddgame).team_arena.team_count = 0;
+    // init_field_72a4 = weapon_slots[754] (arena+0x2A7C)
+    (*ddgame).team_arena.weapon_slots[754] = 0;
 
     // InitRenderIndices — original sets ESI = ddgame + 0x72D8, now uses typed DDGame ptr
     ddgame_init_render_indices(ddgame);

crates/openwa-wormkit/src/replacements/weapon.rs

@@ -395,29 +395,29 @@ unsafe fn fire_weapon_special(
 
 /// Skip Go (subtype 19) — pure Rust replacement for 0x51E8C0.
 ///
-/// Toggles a bit in the team's arena state flags (DDGame+0x4628 + team*0x51C).
-/// Bit position from weapon entry's fire_params field.
+/// Toggles a bit in the team's arena state flags (first DWORD of each team's
+/// region in TeamArenaState). Bit position from weapon entry's fire_params.
 /// If game_version > 0x1C and bit already set: clears it. Otherwise: sets it.
 unsafe fn fire_skip_go(worm: *const CTaskWorm, entry: *const WeaponEntry) {
     use openwa_core::engine::DDGame;
-    use openwa_core::engine::GameInfo;
 
-    let ddgame = (*worm).base.base.ddgame as *const DDGame;
-    let game_info = (*ddgame).game_info as *const GameInfo;
-    let game_version = (*game_info).game_version;
+    let ddgame = &mut *((*worm).base.base.ddgame as *mut DDGame);
+    let game_version = (*ddgame.game_info).game_version;
     let team_index = (*worm).team_index as usize;
 
     let bit_index = (*entry).fire_params._data[0] & 0x1F;
     let bit = 1u32 << bit_index;
 
-    // Team arena flags at DDGame+0x4628 + team_index * 0x51C
-    let flags_ptr = (ddgame as *mut u8).add(0x4628 + team_index * 0x51C) as *mut u32;
+    // First DWORD of each team's region in TeamArenaState (stride 0x51C)
+    let flags_ptr = ddgame.team_arena._teams_region
+        [team_index * 0x51C..][..4]
+        .as_ptr() as *mut u32;
     let flags = *flags_ptr;
 
     if game_version > 0x1C && (flags & bit) != 0 {
-        *flags_ptr = flags & !bit; // clear
+        *flags_ptr = flags & !bit;
     } else {
-        *flags_ptr = flags | bit; // set
+        *flags_ptr = flags | bit;
     }
 }