diff --git a/src/app/combat/PlayerHP.affine b/src/app/combat/PlayerHP.affine
new file mode 100644
index 00000000..929a379a
--- /dev/null
+++ b/src/app/combat/PlayerHP.affine
@@ -0,0 +1,141 @@
+// SPDX-License-Identifier: AGPL-3.0-or-later
+//
+// PlayerHP — health, invincibility frames, knockback.
+//
+// Translated from src/app/combat/PlayerHP.res (Wave 3 second proof, 2026-05-02).
+// See lesson at affinescript/docs/guides/lessons/migrations/idaptik-player-hp.adoc
+// for the re-decomposition rationale.
+//
+// === Re-decompositions vs the ReScript original ===
+// 1. The single mutable record with six fields is fissioned into three aspect
+//    structs (HP, IFrames, Knockback) composed in a parent Player.
+// 2. Same-typed labelled args (~fromX, ~playerX) become a Pos struct.
+// 3. Module-level tuning constants (Damage.roboDogContact, Knockback.speed,
+//    etc.) become no-arg fns rather than `static let` — v0.1.0 has no module
+//    const surface I have verified; using fns avoids the question and is
+//    inlinable by the compiler.
+//
+// === v0.1.0 EXPEDIENT: Int instead of Float ===
+// Float arithmetic is unsupported by v0.1.0's operators (see Hitbox.affine
+// and the hitbox lesson). HP is in tenths (max baseline 1000 = 100.0 HP);
+// timers in milliseconds (1000ms = 1.0s). Damage values rescale by 10.
+//
+// === v0.1.0 EXPEDIENT: immutable returning-new instead of `mut Player` ===
+// The lesson's design specifies `take_damage(p: mut Player, ...)`. v0.1.0
+// has `mut` parameters (see examples/ownership.affine) but the assignment
+// surface for mutating struct fields through a `mut` borrow is not yet
+// verified. This version returns a fresh Player; rewrite when the mut +
+// assignment idiom is confirmed.
+
+struct HP {
+  current: Int,
+  max: Int
+}
+
+struct IFrames {
+  remaining_ms: Int
+}
+
+struct Knockback {
+  vel_x: Int,
+  vel_y: Int,
+  remaining_ms: Int
+}
+
+struct Player {
+  hp: HP,
+  iframes: IFrames,
+  knockback: Knockback
+}
+
+struct Pos {
+  x: Int
+}
+
+struct Velocity {
+  x: Int,
+  y: Int
+}
+
+struct UpdateResult {
+  player: Player,
+  velocity: Velocity
+}
+
+// Tuning constants as no-arg fns.
+fn knockback_speed() -> Int { 200 }
+fn knockback_duration_ms() -> Int { 300 }
+fn iframe_duration_ms() -> Int { 1000 }
+fn knockback_pop_y() -> Int { 0 - 80 }
+
+fn max(a: Int, b: Int) -> Int {
+  if a > b { a } else { b }
+}
+
+// CON is a 0-200 scaling factor; baseline 100 → 1000 (= 100.0 HP in tenths).
+fn make(con: Int) -> Player {
+  let max_hp = 800 + 2 * con;
+  {
+    hp: { current: max_hp, max: max_hp },
+    iframes: { remaining_ms: 0 },
+    knockback: { vel_x: 0, vel_y: 0, remaining_ms: 0 }
+  }
+}
+
+fn is_invincible(p: Player) -> Bool {
+  p.iframes.remaining_ms > 0
+}
+
+fn is_alive(p: Player) -> Bool {
+  p.hp.current > 0
+}
+
+// take_damage returns a fresh Player (see header note on mut).
+fn take_damage(p: Player, amount: Int, source: Pos, player: Pos) -> Player {
+  if is_invincible(p) {
+    p
+  } else {
+    let new_current = max(0, p.hp.current - amount);
+    let direction = if player.x >= source.x { 1 } else { 0 - 1 };
+    {
+      hp: { current: new_current, max: p.hp.max },
+      iframes: { remaining_ms: iframe_duration_ms() },
+      knockback: {
+        vel_x: direction * knockback_speed(),
+        vel_y: knockback_pop_y(),
+        remaining_ms: knockback_duration_ms()
+      }
+    }
+  }
+}
+
+fn update(p: Player, dt_ms: Int) -> UpdateResult {
+  let new_iframe = if p.iframes.remaining_ms > 0 {
+    max(0, p.iframes.remaining_ms - dt_ms)
+  } else {
+    0
+  };
+  let new_kb_remaining = if p.knockback.remaining_ms > 0 {
+    max(0, p.knockback.remaining_ms - dt_ms)
+  } else {
+    0
+  };
+  let emit_velocity = if p.knockback.remaining_ms > 0 {
+    { x: p.knockback.vel_x, y: p.knockback.vel_y }
+  } else {
+    { x: 0, y: 0 }
+  };
+  let new_kb = if new_kb_remaining <= 0 {
+    { vel_x: 0, vel_y: 0, remaining_ms: 0 }
+  } else {
+    { vel_x: p.knockback.vel_x, vel_y: p.knockback.vel_y, remaining_ms: new_kb_remaining }
+  };
+  {
+    player: {
+      hp: p.hp,
+      iframes: { remaining_ms: new_iframe },
+      knockback: new_kb
+    },
+    velocity: emit_velocity
+  }
+}
diff --git a/src/app/combat/PlayerHP.wasm b/src/app/combat/PlayerHP.wasm
new file mode 100644
index 00000000..994c105a
Binary files /dev/null and b/src/app/combat/PlayerHP.wasm differ