Index: src/cui_auto_main.d
==================================================================
--- src/cui_auto_main.d
+++ src/cui_auto_main.d
@@ -4,13 +4,11 @@
 import driver;
 import solver;
 
 class CUI(Solver) : GameObserver
 {
-	this(const(Game) g) {
-		solver = new Solver(g);
-	}
+	this(in Game g) { solver = new Solver(g); }
 	Solver solver;
 	bool fin;
 	override void on_game_changed(char c, const(Game) g, bool finished)
 	{
 		fin = finished;

Index: src/game.d
==================================================================
--- src/game.d
+++ src/game.d
@@ -6,11 +6,11 @@
 {
 	public immutable int y, x;
 	mixin DeriveCreate;
 	mixin DeriveCompare;
 	mixin DeriveShow;
-	Pos clone() const { return new Pos(y, x); }
+	Pos clone() const { return cast(Pos) this; }
 
 @property:
 	Pos wait()  { return this.clone(); }
 	Pos up()    { return new Pos(y+1, x); }
 	Pos down()  { return new Pos(y-1, x); }
@@ -43,11 +43,11 @@
 {
 	public immutable int base, pace;
 	mixin DeriveCreate;
 	mixin DeriveCompare;
 	mixin DeriveShow;
-	Water clone() const { return new Water(base, pace); }
+	Water clone() const { return cast(Water)this; }
 
 	static load(string[string] params)
 	{
 		return new Water(
 			params.get("Water",    "0").to!int(),
@@ -102,11 +102,11 @@
 	Pos robot;
 	Pos lift;
 	int waterproof;
 
 	Map clone() const { return new Map(this); }
-	this(const(Map) m) {
+	this(in Map m) {
 		foreach(s; m.data)
 			this.data ~= s.dup;
 		this.robot = m.robot.clone();
 		this.lift = m.lift.clone();
 		this.waterproof = m.waterproof;
@@ -304,11 +304,11 @@
 		this.map = Map.load(raw_data, params);
 		this.water = Water.load(params);
 	}
 
 	Game clone() const { return new Game(this); }
-	this(const(Game) g) {
+	this(in Game g) {
 		map = g.map.clone();
 		water = g.water.clone();
 		turn = g.turn;
 		dead = g.dead;
 		lambda = g.lambda;

Index: src/gui.d
==================================================================
--- src/gui.d
+++ src/gui.d
@@ -3,11 +3,11 @@
 import game;
 import driver;
 
 class GUI(Solver) : Form, GameObserver
 {
-	this(const(Game) g)
+	this(in Game g)
 	{
 		this.solver = new Solver(g);
 		setup_size(g.map.W, g.map.H);
 		setup_resources();
 		setup_keyhandling();

Index: src/output.d
==================================================================
--- src/output.d
+++ src/output.d
@@ -3,33 +3,33 @@
 import driver;
 import core.stdc.signal;
 
 class NilOutput : GameObserver
 {
-	this(const(Game) g) {}
-	override void on_game_changed(char c, const(Game) g, bool finished) {}
+	this(in Game g) {}
+	override void on_game_changed(char c, in Game g, bool finished) {}
 }
 
 class StdOutput : GameObserver
 {
-	this(const(Game) g) {}
-	override void on_game_changed(char c, const(Game) g, bool finished)
+	this(in Game g) {}
+	override void on_game_changed(char c, in Game g, bool finished)
 	{
 		stdout.write(c);
 		stdout.flush();
 	}
 }
 
 class GuardedOutput : GameObserver
 {
-	this(const(Game) g)
+	this(in Game g)
 	{
 		setup_sigint_handling();
 		ideal_log ~= g.score_if_abort_now;
 	}
 
-	override void on_game_changed(char c, const(Game) g, bool finished)
+	override void on_game_changed(char c, in Game g, bool finished)
 	{
 		log ~= c;
 		score_log ~= g.score;
 		ideal_log ~= g.score_if_abort_now;
 		if(finished)