From 45bec8812c9d5aa1065cf36a8ca878fda5a6b325 Mon Sep 17 00:00:00 2001
From: batsumaru <>
Date: Wed, 19 Aug 2026 20:38:28 +0900
Subject: Added SimState

---
 include/fixed_point.h |  3 ++-
 include/sim_core.h    | 17 +++++++++++++++++
 src/fixed_point.cpp   |  4 ----
 src/sim_core.cpp      |  0
 4 files changed, 19 insertions(+), 5 deletions(-)
 create mode 100644 include/sim_core.h
 create mode 100644 src/sim_core.cpp

diff --git a/include/fixed_point.h b/include/fixed_point.h
index 385ccc2..2a9ec8d 100644
--- a/include/fixed_point.h
+++ b/include/fixed_point.h
@@ -3,6 +3,7 @@
 
 #include <cstdint>
 #include <type_traits>
+#include <compare>
 
 struct fp_t {
     static constexpr std::int32_t Q = 16;
@@ -16,7 +17,7 @@ struct fp_t {
     fp_t operator-(const fp_t& other) const;
     fp_t operator*(const fp_t& other) const;
     fp_t operator/(const fp_t& other) const;
-    bool operator==(const fp_t& other) const;
+    auto operator<=>(const fp_t&) const = default;
 };
 
 static_assert(std::is_trivially_copyable_v<fp_t>, "fp_t must remain trivially copyable for rollback determinism");
diff --git a/include/sim_core.h b/include/sim_core.h
new file mode 100644
index 0000000..88533d0
--- /dev/null
+++ b/include/sim_core.h
@@ -0,0 +1,17 @@
+#ifndef SIM_CORE_H
+#define SIM_CORE_H
+
+#include <type_traits>
+#include "fixed_point.h"
+
+struct SimState {
+    fp_t stage_width;
+    fp_t stage_height;
+    fp_t camera_x;
+    fp_t camera_y;
+};
+
+static_assert(std::is_trivially_copyable_v<SimState>, "SimState must be trivially copyable for rollback");
+static_assert(sizeof(SimState) == 16, "SimState size changed unexpectedly");
+
+#endif // !SIM_CORE_H
diff --git a/src/fixed_point.cpp b/src/fixed_point.cpp
index a39f2bc..3a69958 100644
--- a/src/fixed_point.cpp
+++ b/src/fixed_point.cpp
@@ -39,7 +39,3 @@ fp_t fp_t::operator/(const fp_t& other) const {
     }
     return {static_cast<std::int32_t>(temp)};
 }
-
-bool fp_t::operator==(const fp_t& other) const {
-    return raw == other.raw;
-}
diff --git a/src/sim_core.cpp b/src/sim_core.cpp
new file mode 100644
index 0000000..e69de29
-- 
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