diff --git a/original/MECHANICS_PROGRESS.md b/original/MECHANICS_PROGRESS.md
index c794701..141c707 100644
--- a/original/MECHANICS_PROGRESS.md
+++ b/original/MECHANICS_PROGRESS.md
@@ -105,7 +105,8 @@ The executable image remains unchanged; only the current disposable Wine
 process is modified. Run the injector while the ball is waiting in the launcher
 so it can identify the live game object, or supply the previously reported
 `--object-base` to both the injector and tracer during a sequence of active
-probes.
+probes. `--substeps 1` isolates one collision integration step; omitting it
+retains the original configured detail level.
 
 A probe at `(289,94)` captured the original terminal-18 path. The collision
 suspended the ball while frames advanced from 10 through 18 at the configured
@@ -113,3 +114,11 @@ suspended the ball while frames advanced from 10 through 18 at the configured
 then cleared suspension during the same timer callback. The three default
 physics substeps each added 15 millipixels of vertical velocity, confirming the
 observed total gravity increment of 45 per timer tick.
+
+A one-substep probe against the vertical shooter walls recovered the type-2
+response arithmetic. For unit tangent `t` from the registered start to end and
+left normal `n`, an incoming contact with `vn = dot(v,n)` and `vt = dot(v,t)`
+uses `vn' = -0.6 * vn` and `vt' = vt + 0.1 * vn` for the ordinary rail
+coefficients stored in its two Real48 fields. The new position is the previous
+position plus this response velocity; the original does not separate a circle
+from the line with a modern capsule solver.
diff --git a/original/tools/inject_original_state.py b/original/tools/inject_original_state.py
index 8b0d816..412e0cb 100755
--- a/original/tools/inject_original_state.py
+++ b/original/tools/inject_original_state.py
@@ -18,6 +18,7 @@ from trace_original_state import (
     NEXT_BALL_Y,
     OBJECT_BALL_X,
     OBJECT_BALL_Y,
+    PHYSICS_SUBSTEPS,
     PREVIOUS_BALL_X,
     PREVIOUS_BALL_Y,
     VELOCITY_X,
@@ -49,6 +50,12 @@ def parse_args() -> argparse.Namespace:
     parser.add_argument("--y", type=float, required=True, help="ball center y in logical pixels")
     parser.add_argument("--vx", type=float, default=0.0, help="x velocity in pixels per timer tick")
     parser.add_argument("--vy", type=float, default=0.0, help="y velocity in pixels per timer tick")
+    parser.add_argument(
+        "--substeps",
+        type=int,
+        choices=range(1, 6),
+        help="temporarily force the original physics substep count",
+    )
     return parser.parse_args()
 
 
@@ -106,6 +113,8 @@ def main() -> None:
                 (NEXT_BALL_Y, next_y),
             ):
                 memory.write(data_base + offset, value)
+            if args.substeps is not None:
+                memory.write(data_base + PHYSICS_SUBSTEPS, struct.pack("<H", args.substeps))
             for offset, value in (
                 (VELOCITY_X, velocity_x),
                 (VELOCITY_Y, velocity_y),
diff --git a/original/tools/trace_original_state.py b/original/tools/trace_original_state.py
index d45e8ec..07a779c 100755
--- a/original/tools/trace_original_state.py
+++ b/original/tools/trace_original_state.py
@@ -31,8 +31,12 @@ CLAW_FRAME = 0x086D
 CLAW_TARGET_FRAME = 0x086F
 CLAW_SPRITE_BANK = 0x0873
 CLAW_ANIMATION_BLOCKED = 0x0874
+PHYSICS_SUBSTEPS = 0x0871
 
 # Recovered offsets in the live game-window object.
+MAXIMUM_SPEED = 0x0056
+GRAVITY_PER_SUBSTEP = 0x005A
+ACTIVE_BALL_COUNT = 0x0061
 VELOCITY_X = 0x0BAA
 VELOCITY_Y = 0x0BAE
 PREVIOUS_BALL_X = 0x0BBA
@@ -44,6 +48,8 @@ RIGHT_FLIPPER_POSITION = 0x0BD6
 LEFT_FLIPPER_DOWN = 0x0BDA
 RIGHT_FLIPPER_DOWN = 0x0BDB
 BALL_SUSPENDED = 0x0BDF
+BALL_ACTIVE = 0x0BDD
+COLLISION_DISABLED = 0x0BD8
 OBJECT_READ_SIZE = 0x0BE0
 
 
@@ -208,6 +214,10 @@ CSV_FIELDS = [
     "elapsed_us",
     "player_count",
     "current_player",
+    "physics_substeps",
+    "active_ball_count",
+    "maximum_speed_milli_per_tick",
+    "gravity_milli_per_substep",
     "ball_x_milli",
     "ball_y_milli",
     "next_ball_x_milli",
@@ -222,6 +232,8 @@ CSV_FIELDS = [
     "right_flipper_position",
     "left_flipper_down",
     "right_flipper_down",
+    "ball_active",
+    "collision_disabled",
     "ball_suspended",
     "claw_active",
     "claw_frame",
@@ -235,6 +247,10 @@ def sample_state(data: bytes, obj: bytes) -> tuple[int, ...]:
     return (
         data[PLAYER_COUNT],
         data[CURRENT_PLAYER],
+        unpack_u16(data, PHYSICS_SUBSTEPS),
+        obj[ACTIVE_BALL_COUNT],
+        unpack_i32(obj, MAXIMUM_SPEED),
+        unpack_i32(obj, GRAVITY_PER_SUBSTEP),
         unpack_i32(data, BALL_X),
         unpack_i32(data, BALL_Y),
         unpack_i32(data, NEXT_BALL_X),
@@ -249,6 +265,8 @@ def sample_state(data: bytes, obj: bytes) -> tuple[int, ...]:
         unpack_u16(obj, RIGHT_FLIPPER_POSITION),
         obj[LEFT_FLIPPER_DOWN],
         obj[RIGHT_FLIPPER_DOWN],
+        obj[BALL_ACTIVE],
+        obj[COLLISION_DISABLED],
         obj[BALL_SUSPENDED],
         data[CLAW_ACTIVE],
         unpack_u16(data, CLAW_FRAME),