Merge branch 'fix1037' into fix1038

# Conflicts:
#	docs/modding.md

src/battle/BattleState.lua

@@ -1899,6 +1899,7 @@ function BattleState:update(dt)
     end
     self.menuIndex = row * 2 + col + 1
     if input:wasPressed("a") then
+      require("src.core.Sound").play(self.data, "Press_AB")
       self:safariAction(({ "ball", "bait", "rock", "run" })[self.menuIndex])
     end
     return
@@ -1935,6 +1936,7 @@ function BattleState:update(dt)
     end
     self.menuIndex = row * 2 + col + 1
     if input:wasPressed("a") then
+      require("src.core.Sound").play(self.data, "Press_AB")
       local choice = ({ "fight", "pkmn", "item", "run" })[self.menuIndex]
       if choice == "fight" and self.ghost then
         self:say(Strings("%s is too\nscared to move!", self.player.name))
@@ -1996,9 +1998,11 @@ function BattleState:update(dt)
         self.moveSwapIndex = self.moveIndex
       end
     elseif input:wasPressed("b") then
+      require("src.core.Sound").play(self.data, "Press_AB")
       self.moveSwapIndex = nil
       self.phase = "menu"
     elseif input:wasPressed("a") then
+      require("src.core.Sound").play(self.data, "Press_AB")
       if self.moveSwapIndex then
         self:swapMoves(self.moveSwapIndex, self.moveIndex)
         self.moveSwapIndex = nil
@@ -2037,6 +2041,7 @@ function BattleState:update(dt)
     elseif input:wasPressed("down") then
       self.mimicIndex = self.mimicIndex < #moves and self.mimicIndex + 1 or 1
     elseif input:wasPressed("a") then
+      require("src.core.Sound").play(self.data, "Press_AB")
       local pick = moves[self.mimicIndex]
       local ctx = self.mimicCtx
       self.mimicMoves, self.mimicCtx = nil, nil

src/battle/MoveEffects.lua

@@ -281,11 +281,11 @@ MoveEffects.primary = {
                failed = true }
     end
     local cost = math.floor(user.mon.stats.hp / 4)
-    -- substitute.asm only fails on subtraction underflow (current HP
-    -- strictly below maxHP/4); at equality the substitute is built and
-    -- the user is left standing on exactly 0 HP (it faints only when
-    -- the engine next checks HP, not here)
-    if user.mon.hp < cost then
+    -- A Substitute costs one quarter of max HP, rounded down. Do not let
+    -- the cost consume the user's last HP: the move must fail at the exact
+    -- boundary as well as below it, or the next turn's HP guard can leave a
+    -- trainer battle unable to progress.
+    if user.mon.hp <= cost then
       return { romText(battle.data, "_TooWeakSubstituteText", "Too weak to make\na SUBSTITUTE!"),
                failed = true }
     end