Old changesHEADmaster

25 files changed, 597 insertions, 257 deletions

diff --git a/Djup.Native/Constants.cs b/Djup.Native/Constants.cs
new file mode 100644
index 0000000..90692be
--- /dev/null
+++ b/Djup.Native/Constants.cs
@@ -0,0 +1,7 @@
+namespace Djup.Native;
+
+public static class Constants
+{
+    public const int WorldMaxPlayers = 5;
+    public const int WorldMaxBullets = 5000;
+}
diff --git a/Djup.Native/LibDjup.cs b/Djup.Native/LibDjup.cs
index 0b4a3db..15dcdad 100644
--- a/Djup.Native/LibDjup.cs
+++ b/Djup.Native/LibDjup.cs
@@ -31,21 +31,24 @@ public static partial class LibDjup
     [LibraryImport(LibraryName, EntryPoint = Prefix + nameof(log_set_level))]
     public static partial Vec2 log_set_level(LogLevel minLevel);
 
-    [LibraryImport(LibraryName, EntryPoint = Prefix + nameof(world_create))]
-    public static partial IntPtr world_create();
+    [LibraryImport(LibraryName, EntryPoint = Prefix + nameof(physics_context_create))]
+    public static partial IntPtr physics_context_create(uint snapshots);
 
-    [LibraryImport(LibraryName, EntryPoint = Prefix + nameof(world_free))]
-    public static partial void world_free(IntPtr world);
+    [LibraryImport(LibraryName, EntryPoint = Prefix + nameof(physics_context_free))]
+    public static partial void physics_context_free(IntPtr context);
 
-    [LibraryImport(LibraryName, EntryPoint = Prefix + nameof(world_create_entity))]
-    public static partial int world_create_entity(IntPtr world, EntityKind kind);
+    [LibraryImport(LibraryName, EntryPoint = Prefix + nameof(physics_context_get_snapshot))]
+    public static partial IntPtr physics_context_get_snapshot(IntPtr context);
 
-    [LibraryImport(LibraryName, EntryPoint = Prefix + nameof(world_find_entity))]
-    public static unsafe partial Entity* world_find_entity(IntPtr world, int entityId);
+    [LibraryImport(LibraryName, EntryPoint = Prefix + nameof(physics_context_return_snapshot))]
+    public static partial void physics_context_return_snapshot(IntPtr context, IntPtr snapshot);
 
-    [LibraryImport(LibraryName, EntryPoint = Prefix + nameof(world_remove_entity))]
-    public static partial void world_remove_entity(IntPtr world, int entityId);
+    [LibraryImport(LibraryName, EntryPoint = Prefix + nameof(physics_tick))]
+    public static partial int physics_tick(IntPtr currentSnapshot, double delta, IntPtr nextSnapshot);
 
-    [LibraryImport(LibraryName, EntryPoint = Prefix + nameof(world_tick))]
-    public static partial int world_tick(IntPtr world, double delta);
+    [LibraryImport(LibraryName, EntryPoint = Prefix + nameof(snapshot_put_player))]
+    public static unsafe partial int snapshot_put_player(IntPtr snapshot, uint playerId, Player *player);
+
+    [LibraryImport(LibraryName, EntryPoint = Prefix + nameof(snapshot_set_player_input))]
+    public static partial int snapshot_set_player_input(IntPtr snapshot, uint playerId, byte input);
 }
diff --git a/Djup.Native/Types.cs b/Djup.Native/Types.cs
index 478208f..7d9c41e 100644
--- a/Djup.Native/Types.cs
+++ b/Djup.Native/Types.cs
@@ -1,4 +1,5 @@
 using System.Diagnostics;
+using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 
 namespace Djup.Native;
@@ -21,29 +22,60 @@ public struct Vec2
     public override string ToString() => $"({X}, {Y})";
 }
 
-public enum EntityKind
+public enum EntityState : byte
 {
-    None = 0,
-    Ball
+    Inactive = 0,
+    Active,
+    Removed,
+    Dead
 }
 
-[StructLayout(LayoutKind.Explicit)]
-public struct Entity
+public enum PlayerInput : byte
 {
-    [FieldOffset(0)]
-    public EntityKind kind;
+    Up = 1 << 0,
+    Down = 1 << 1,
+    Left = 1 << 2,
+    Right = 1 << 3
+}
 
-    [FieldOffset(4)]
-    public Ball ball;
+[StructLayout(LayoutKind.Sequential)]
+public struct Player
+{
+    public EntityState State { get; }
+    private byte input;
+    public Vec2 Position { get; set; }
+    public Vec2 Velocity { get; set; }
 }
 
 [StructLayout(LayoutKind.Sequential)]
-public struct Ball
+public struct Bullet
 {
+    public EntityState State { get; set; }
     public Vec2 Position { get; set; }
     public Vec2 Velocity { get; set; }
 }
 
+[StructLayout(LayoutKind.Sequential)]
+public struct Snapshot
+{
+    [InlineArray(Constants.WorldMaxPlayers)]
+    public struct PlayerArray
+    {
+        private Player _element0;
+    }
+
+    [InlineArray(Constants.WorldMaxBullets)]
+    public struct BallArray
+    {
+        private Bullet _element0;
+    }
+
+    private byte active;
+    public uint Tick { get; }
+    public PlayerArray Players { get; }
+    public BallArray Bullets { get; }
+}
+
 public enum LogLevel
 {
     Trace,
diff --git a/client/Game.cs b/client/Game.cs
new file mode 100644
index 0000000..6bf6192
--- /dev/null
+++ b/client/Game.cs
@@ -0,0 +1,37 @@
+using Godot;
+using System;
+using Djup.Native;
+
+public partial class Game : Node2D
+{
+	private World world;
+
+	private int[] balls = new int[100];
+	private Random rng = new();
+
+	// Called when the node enters the scene tree for the first time.
+	public unsafe override void _Ready()
+	{
+		RenderingServer.SetDefaultClearColor(Colors.LightGray);
+		LibDjup.log_set_output((level, source, line, msg) => {
+			string level_name = level switch
+			{
+				LogLevel.Trace => "trace",
+				LogLevel.Debug => "debug",
+				LogLevel.Info =>  " info",
+				LogLevel.Warn =>  " warn",
+				LogLevel.Error => "error",
+				LogLevel.Fatal => "fatal",
+				_ => "UNKNOWN"
+			};
+			GD.Print($"libdjup {source.PadLeft(10)}:{line.ToString().PadRight(3)} {level_name}: {msg}");
+		});
+
+		world = GetNode<World>("World");
+
+		world.PutPlayer(0, new Djup.Native.Player()
+		{
+			Position = new Vec2(100f, 100f),
+		});
+	}
+}
diff --git a/client/Player.cs b/client/Player.cs
new file mode 100644
index 0000000..da95275
--- /dev/null
+++ b/client/Player.cs
@@ -0,0 +1,24 @@
+using Godot;
+using System;
+using Djup.Native;
+
+public partial class Player : Node2D
+{
+	[Export]
+	public World World { get; set; }
+	public uint Id { get; set; } = 0;
+
+	public unsafe override void _Process(double delta)
+	{
+		byte input = 0;
+		if (Input.IsActionPressed("up"))
+			input |= (byte)PlayerInput.Up;
+		if (Input.IsActionPressed("down"))
+			input |= (byte)PlayerInput.Down;
+		if (Input.IsActionPressed("left"))
+			input |= (byte)PlayerInput.Left;
+		if (Input.IsActionPressed("right"))
+			input |= (byte)PlayerInput.Right;
+		World.SetPlayerInput(Id, input);
+	}
+}
diff --git a/client/Root.cs b/client/Root.cs
deleted file mode 100644
index dfbf0da..0000000
--- a/client/Root.cs
+++ /dev/null
@@ -1,87 +0,0 @@
-using Godot;
-using System;
-using Djup.Native;
-
-public partial class Root : Node2D
-{
-	private IntPtr native_world;
-	private int[] balls = new int[100];
-	private Random rng = new();
-	private const double Tps = 1d/60d;
-	
-	// Called when the node enters the scene tree for the first time.
-	public unsafe override void _Ready()
-	{
-		RenderingServer.SetDefaultClearColor(Colors.LightGray);
-		LibDjup.log_set_output((level, source, line, msg) => {
-			string level_name = level switch
-			{
-				LogLevel.Trace => "trace",
-				LogLevel.Debug => "debug",
-				LogLevel.Info => "info",
-				LogLevel.Warn => "warn",
-				LogLevel.Error => "error",
-				LogLevel.Fatal => "fatal" 
-			};
-			GD.Print($"libdjup {source}:{line} {level_name.PadLeft(5, ' ')}: {msg}");
-		});
-
-		native_world = LibDjup.world_create();
-		for (int i = 0; i < balls.Length; i++)
-		{
-			int id = LibDjup.world_create_entity(native_world, EntityKind.Ball);
-			if (id < 0)
-			{
-				throw new Exception("Failed to create entity");
-			}
-			balls[i] = id;
-			Entity *ent;
-			var pos = new Vec2(5f * rng.Next(10), 5f * rng.Next(20));
-			var vel = LibDjup.vec2_mul(LibDjup.vec2_normal(new Vec2(50f + 5f * rng.Next(10), 50f)), 25.0f);
-			GD.Print(vel, " --> ", LibDjup.vec2_length(vel));
-			ent = LibDjup.world_find_entity(native_world, balls[i]);
-			ent->ball.Position = pos;
-			ent->ball.Velocity = vel;
-		}
-	}
-
-	public override void _ExitTree()
-	{
-		LibDjup.world_free(native_world);
-	}
-
-	private void DrawBall(Ball ball)
-	{
-		//Color color = rng.Next(5) switch
-		//{
-			//0 => Colors.Black,
-			//1 => Colors.Blue,
-			//2 => Colors.Red,
-			//3 => Colors.Green,
-			//4 => Colors.Pink
-		//};
-		Color color = Colors.Blue;
-		this.DrawCircle(new Vector2(ball.Position.X, ball.Position.Y), 5f, color, antialiased: true);
-	}
-
-	public unsafe override void _Draw()
-	{
-		for (int i = 0; i < balls.Length; i++)
-		{
-			DrawBall(LibDjup.world_find_entity(native_world, balls[i])->ball);
-		}
-	}
-
-	public override void _Process(double delta)
-	{
-		this.QueueRedraw();
-	}
-	
-	public override void _PhysicsProcess(double delta)
-	{
-		if (LibDjup.world_tick(native_world, Tps) != 0)
-		{
-			GD.Print("world_tick failed");
-		}
-	}
-}
diff --git a/client/World.cs b/client/World.cs
new file mode 100644
index 0000000..8f5dfb6
--- /dev/null
+++ b/client/World.cs
@@ -0,0 +1,75 @@
+using Godot;
+using System;
+using Djup.Native;
+
+public partial class World : Node2D
+{
+	private IntPtr context;
+	private IntPtr currentSnapshot;
+	public const double Tps = 1d/60d;
+
+	public unsafe override void _Ready()
+	{
+		context = LibDjup.physics_context_create(2);
+		currentSnapshot = LibDjup.physics_context_get_snapshot(context);
+	}
+
+	public override void _ExitTree()
+	{
+		LibDjup.physics_context_free(context);
+	}
+
+	public unsafe void PutPlayer(uint id, Djup.Native.Player player)
+	{
+		if (LibDjup.snapshot_put_player(currentSnapshot, id, &player) != 0)
+		{
+			throw new Exception($"Failed to put player {id}");
+		}
+	}
+
+	public void SetPlayerInput(uint playerId, byte input)
+	{
+		int ret = LibDjup.snapshot_set_player_input(currentSnapshot, playerId, input);
+		if (ret != 0)
+		{
+			throw new Exception($"Failed to set input of player {playerId}: {ret}");
+		}
+	}
+
+	private unsafe void DrawPlayer(Djup.Native.Player player)
+	{
+		float radius = 50f;
+		this.DrawCircle(new Vector2(player.Position.X, player.Position.Y), radius, Colors.DarkBlue, antialiased: true);
+		this.DrawCircle(new Vector2(player.Position.X, player.Position.Y), radius * 0.90f, Colors.Blue, antialiased: true);
+	}
+
+	public unsafe override void _Draw()
+	{
+		Snapshot *s = (Snapshot *)currentSnapshot;
+
+		for (int i = 0; i < Constants.WorldMaxPlayers; i++)
+		{
+			var p = s->Players[i];
+			if (p.State == EntityState.Active)
+			{
+				DrawPlayer(p);
+			}
+		}
+	}
+
+	public override void _Process(double delta)
+	{
+		this.QueueRedraw();
+	}
+
+	public override void _PhysicsProcess(double delta)
+	{
+		IntPtr next = LibDjup.physics_context_get_snapshot(context);
+		if (LibDjup.physics_tick(currentSnapshot, Tps, next) != 0)
+		{
+			throw new Exception("World tick failed");
+		}
+		LibDjup.physics_context_return_snapshot(context, currentSnapshot);
+		currentSnapshot = next;
+	}
+}
diff --git a/client/game.tscn b/client/game.tscn
new file mode 100644
index 0000000..4ec7809
--- /dev/null
+++ b/client/game.tscn
@@ -0,0 +1,13 @@
+[gd_scene load_steps=4 format=3 uid="uid://w0k2j13hm04i"]
+
+[ext_resource type="Script" path="res://Game.cs" id="1_t8lam"]
+[ext_resource type="PackedScene" uid="uid://drdk1by1fun2q" path="res://world.tscn" id="2_tm4sj"]
+[ext_resource type="PackedScene" uid="uid://b0f23dtef1o4h" path="res://player.tscn" id="3_caccr"]
+
+[node name="Game" type="Node2D"]
+script = ExtResource("1_t8lam")
+
+[node name="World" parent="." instance=ExtResource("2_tm4sj")]
+
+[node name="Player" parent="." node_paths=PackedStringArray("World") instance=ExtResource("3_caccr")]
+World = NodePath("../World")
diff --git a/client/player.tscn b/client/player.tscn
new file mode 100644
index 0000000..b1f9f5f
--- /dev/null
+++ b/client/player.tscn
@@ -0,0 +1,6 @@
+[gd_scene load_steps=2 format=3 uid="uid://b0f23dtef1o4h"]
+
+[ext_resource type="Script" path="res://Player.cs" id="1_bjul0"]
+
+[node name="Player" type="Node2D"]
+script = ExtResource("1_bjul0")
diff --git a/client/project.godot b/client/project.godot
index 6107d87..403aac4 100644
--- a/client/project.godot
+++ b/client/project.godot
@@ -11,7 +11,7 @@ config_version=5
 [application]
 
 config/name="Djup"
-run/main_scene="res://root.tscn"
+run/main_scene="res://game.tscn"
 config/features=PackedStringArray("4.3", "C#", "Forward Plus")
 config/icon="res://icon.svg"
 
@@ -22,3 +22,26 @@ window/stretch/mode="canvas_items"
 [dotnet]
 
 project/assembly_name="Djup"
+
+[input]
+
+left={
+"deadzone": 0.5,
+"events": [Object(InputEventKey,"resource_local_to_scene":false,"resource_name":"","device":-1,"window_id":0,"alt_pressed":false,"shift_pressed":false,"ctrl_pressed":false,"meta_pressed":false,"pressed":false,"keycode":0,"physical_keycode":65,"key_label":0,"unicode":97,"location":0,"echo":false,"script":null)
+]
+}
+right={
+"deadzone": 0.5,
+"events": [Object(InputEventKey,"resource_local_to_scene":false,"resource_name":"","device":-1,"window_id":0,"alt_pressed":false,"shift_pressed":false,"ctrl_pressed":false,"meta_pressed":false,"pressed":false,"keycode":0,"physical_keycode":68,"key_label":0,"unicode":100,"location":0,"echo":false,"script":null)
+]
+}
+up={
+"deadzone": 0.5,
+"events": [Object(InputEventKey,"resource_local_to_scene":false,"resource_name":"","device":-1,"window_id":0,"alt_pressed":false,"shift_pressed":false,"ctrl_pressed":false,"meta_pressed":false,"pressed":false,"keycode":0,"physical_keycode":87,"key_label":0,"unicode":119,"location":0,"echo":false,"script":null)
+]
+}
+down={
+"deadzone": 0.5,
+"events": [Object(InputEventKey,"resource_local_to_scene":false,"resource_name":"","device":-1,"window_id":0,"alt_pressed":false,"shift_pressed":false,"ctrl_pressed":false,"meta_pressed":false,"pressed":false,"keycode":0,"physical_keycode":83,"key_label":0,"unicode":115,"location":0,"echo":false,"script":null)
+]
+}
diff --git a/client/root.tscn b/client/root.tscn
deleted file mode 100644
index ded95a0..0000000
--- a/client/root.tscn
+++ /dev/null
@@ -1,6 +0,0 @@
-[gd_scene load_steps=2 format=3 uid="uid://drdk1by1fun2q"]
-
-[ext_resource type="Script" path="res://Root.cs" id="1_p5oo0"]
-
-[node name="Root" type="Node2D"]
-script = ExtResource("1_p5oo0")
diff --git a/client/world.tscn b/client/world.tscn
new file mode 100644
index 0000000..0055d3b
--- /dev/null
+++ b/client/world.tscn
@@ -0,0 +1,6 @@
+[gd_scene load_steps=2 format=3 uid="uid://drdk1by1fun2q"]
+
+[ext_resource type="Script" path="res://World.cs" id="1_7wii1"]
+
+[node name="World" type="Node2D"]
+script = ExtResource("1_7wii1")
diff --git a/lib/build.sh b/lib/build.sh
index f305939..3f8b5a6 100755
--- a/lib/build.sh
+++ b/lib/build.sh
@@ -6,9 +6,9 @@ fail() {
 }
 
 CC=cc
-CFLAGS="-std=c99 -Wall -Wextra -Wpedantic -D_POSIX_C_SOURCE=200809L"
+CFLAGS="-std=c99 -Wall -Wextra -Wpedantic -Og -g -D_POSIX_C_SOURCE=200809L"
 LDFLAGS="-fPIC -lm"
-SOURCES="test.c vec2.c world.c log.c"
+SOURCES="test.c vec2.c snapshot.c log.c player.c physics.c"
 output="build"
 
 for arg ; do
diff --git a/lib/common.h b/lib/common.h
new file mode 100644
index 0000000..d6d8816
--- /dev/null
+++ b/lib/common.h
@@ -0,0 +1 @@
+#define LENGTH(x) (sizeof(x) / sizeof(x[0]))
diff --git a/lib/constants.h b/lib/constants.h
new file mode 100644
index 0000000..817fa43
--- /dev/null
+++ b/lib/constants.h
@@ -0,0 +1,12 @@
+#define WORLD_MAX_PLAYERS 5
+#define WORLD_MAX_BULLETS 5000
+
+#define PLAYER_ACCELERATION 150.0f
+#define PLAYER_DRAG 2.0f
+
+enum {
+	INPUT_UP = 1 << 0,
+	INPUT_DOWN = 1 << 1,
+	INPUT_LEFT = 1 << 2,
+	INPUT_RIGHT = 1 << 3
+};
diff --git a/lib/physics.c b/lib/physics.c
new file mode 100644
index 0000000..adcf433
--- /dev/null
+++ b/lib/physics.c
@@ -0,0 +1,124 @@
+#include <assert.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "common.h"
+#include "player.h"
+#include "snapshot.h"
+#include "types.h"
+
+#include "physics.h"
+
+struct context *
+dp_physics_context_create(size_t snapshots)
+{
+	struct context *ctx = NULL;
+
+	if (!(ctx = malloc(sizeof(*ctx))))
+		return NULL;
+	memset(ctx, 0, sizeof(*ctx));
+
+	ctx->snapshots_len = snapshots;
+	if (!(ctx->snapshots = malloc(sizeof(*ctx->snapshots) * snapshots)))
+	{
+		free(ctx);
+		return NULL;
+	}
+	memset(ctx->snapshots, 0, sizeof(*ctx->snapshots) * snapshots);
+
+	return ctx;
+}
+
+void
+dp_physics_context_free(struct context *ctx)
+{
+	if (!ctx)
+		return;
+	if (ctx->snapshots)
+		free(ctx->snapshots);
+	free(ctx);
+}
+
+struct snapshot *dp_physics_context_get_snapshot(struct context *ctx)
+{
+	size_t i;
+	struct snapshot *s;
+
+	for (i = 0; i < ctx->snapshots_len; i++)
+	{
+		s = &ctx->snapshots[i];
+		if (!s->active)
+		{
+			s->active = true;
+			return s;
+		}
+	}
+	return NULL;
+}
+
+void dp_physics_context_return_snapshot(struct context *ctx, struct snapshot *s)
+{
+	size_t i;
+
+	assert(s->active);
+
+	for (i = 0; i < ctx->snapshots_len; i++)
+	{
+		if (s == &ctx->snapshots[i])
+		{
+			s->active = false;
+		}
+	}
+
+	assert(!s->active);
+}
+
+static void
+dp_physics_tick_player(const struct player *cur, double delta, struct player *next)
+{
+	vec2 acc;
+
+	next->state = cur->state;
+	if (next->state == STATE_REMOVED)
+		next->state = STATE_INACTIVE;
+	if (next->state == STATE_INACTIVE)
+		return;
+
+	acc = dp_player_calculate_acceleration(cur);
+	next->vel = dp_vec2_add(cur->vel, dp_vec2_mul(acc, delta));
+	next->pos = dp_vec2_add(cur->pos, dp_vec2_mul(next->vel, delta));
+}
+
+static void
+dp_physics_tick_ball(const struct ball *cur, double delta, struct ball *next)
+{
+	next->state = cur->state;
+	if (next->state == STATE_REMOVED)
+		next->state = STATE_INACTIVE;
+	if (next->state == STATE_INACTIVE)
+		return;
+
+	next->pos = dp_vec2_add(cur->pos, dp_vec2_mul(cur->vel, delta));
+}
+
+int
+dp_physics_tick(const struct snapshot *cur, double delta, struct snapshot *next)
+{
+	size_t i;
+
+	assert(cur->active);
+	assert(next->active);
+
+	for (i = 0; i < LENGTH(cur->players); i++)
+	{
+		dp_physics_tick_player(&cur->players[i], delta, &next->players[i]);
+	}
+
+	for (i = 0; i < LENGTH(cur->balls); i++)
+	{
+		dp_physics_tick_ball(&cur->balls[i], delta, &next->balls[i]);
+	}
+
+	next->tick = cur->tick + 1;
+	return 0;
+}
diff --git a/lib/physics.h b/lib/physics.h
new file mode 100644
index 0000000..7aa2b31
--- /dev/null
+++ b/lib/physics.h
@@ -0,0 +1,17 @@
+#include "types.h"
+
+struct snapshot;
+
+/* A game world */
+struct context {
+	size_t snapshots_len;
+	struct snapshot *snapshots;
+};
+
+struct context *dp_physics_context_create(size_t snapshots);
+void dp_physics_context_free(struct context *);
+
+struct snapshot *dp_physics_context_get_snapshot(struct context *);
+void dp_physics_context_return_snapshot(struct context *, struct snapshot *);
+
+int dp_physics_tick(const struct snapshot *current, double delta, struct snapshot *next);
diff --git a/lib/player.c b/lib/player.c
new file mode 100644
index 0000000..35c3b80
--- /dev/null
+++ b/lib/player.c
@@ -0,0 +1,36 @@
+#include "snapshot.h"
+
+#include "player.h"
+
+vec2
+dp_player_calculate_acceleration(const struct player *p)
+{
+	vec2 acc, dec;
+	int x = 0, y = 0;
+
+	if (p->input & INPUT_UP)
+	{
+		y -= 1;
+	}
+	if (p->input & INPUT_DOWN)
+	{
+		y += 1;
+	}
+
+	if (p->input & INPUT_LEFT)
+	{
+		x -= 1;
+	}
+	if (p->input & INPUT_RIGHT)
+	{
+		x += 1;
+	}
+
+	acc = dp_vec2_new((float)x, (float)y);
+	acc = dp_vec2_normal(acc);
+	acc = dp_vec2_mul(acc, PLAYER_ACCELERATION);
+
+	dec = dp_vec2_mul(p->vel, -1.0f * PLAYER_DRAG);
+
+	return dp_vec2_add(acc, dec);
+}
diff --git a/lib/player.h b/lib/player.h
new file mode 100644
index 0000000..2f365bf
--- /dev/null
+++ b/lib/player.h
@@ -0,0 +1,5 @@
+#include "types.h"
+
+struct player;
+
+vec2 dp_player_calculate_acceleration(const struct player *);
diff --git a/lib/snapshot.c b/lib/snapshot.c
new file mode 100644
index 0000000..88c17a1
--- /dev/null
+++ b/lib/snapshot.c
@@ -0,0 +1,99 @@
+#include <string.h>
+
+#include "common.h"
+
+#include "snapshot.h"
+
+int dp_snapshot_put_player(struct snapshot *s, uint32_t id, const struct player *p)
+{
+	if (!s || !p)
+		return -1;
+	if (id >= LENGTH(s->players))
+		return -1;
+
+	s->players[id] = *p;
+	s->players[id].state = STATE_ACTIVE;
+	return 0;
+}
+
+struct player *dp_snapshot_get_player(struct snapshot *s, uint32_t id)
+{
+	struct player *p;
+
+	if (!s)
+		return NULL;
+	if (id >= LENGTH(s->players))
+		return NULL;
+
+	p = &s->players[id];
+	if (p->state == STATE_INACTIVE)
+		return NULL;
+	return p;
+}
+
+int dp_snapshot_remove_player(struct snapshot *s, uint32_t id)
+{
+	struct player *p;
+
+	if (!s)
+		return -1;
+	if (id >= LENGTH(s->players))
+		return -1;
+
+	p = dp_snapshot_get_player(s, id);
+	memset(p, 0, sizeof(*p));
+	p->state = STATE_REMOVED;
+	return 0;
+}
+
+int dp_snapshot_set_player_input(struct snapshot *s, uint32_t id, uint8_t input)
+{
+	struct player *p;
+
+	if (!(p = dp_snapshot_get_player(s, id)))
+		return -1;
+	p->input = input;
+	return 0;
+}
+
+int dp_snapshot_put_ball(struct snapshot *s, uint32_t id, const struct ball *b)
+{
+	if (!s || !b)
+		return -1;
+	if (id >= LENGTH(s->balls))
+		return -1;
+
+	s->balls[id] = *b;
+	s->balls[id].state = STATE_ACTIVE;
+	return 0;
+}
+
+struct ball *dp_snapshot_get_ball(struct snapshot *s, uint32_t id)
+{
+	struct ball *b;
+
+	if (!s)
+		return NULL;
+	if (id >= LENGTH(s->balls))
+		return NULL;
+
+	b = &s->balls[id];
+	if (b->state == STATE_INACTIVE)
+		return NULL;
+	return b;
+}
+
+int dp_snapshot_remove_ball(struct snapshot *s, uint32_t id)
+{
+	struct ball *b;
+
+	if (!s)
+		return -1;
+	if (id >= LENGTH(s->balls))
+		return -1;
+
+	b = dp_snapshot_get_ball(s, id);
+	memset(b, 0, sizeof(*b));
+	b->state = STATE_REMOVED;
+	return 0;
+}
diff --git a/lib/snapshot.h b/lib/snapshot.h
new file mode 100644
index 0000000..022d989
--- /dev/null
+++ b/lib/snapshot.h
@@ -0,0 +1,39 @@
+#include "types.h"
+#include "constants.h"
+
+enum {
+	STATE_INACTIVE = 0,
+	STATE_ACTIVE,
+	STATE_REMOVED,
+	STATE_DEAD
+};
+
+struct player {
+	uint8_t state;
+	uint8_t input;
+	char pad[2];
+	vec2 pos;
+	vec2 vel;
+};
+
+struct ball {
+	uint8_t state;
+	vec2 pos;
+	vec2 vel;
+};
+
+struct snapshot {
+	char active;
+	uint32_t tick;
+	struct player players[WORLD_MAX_PLAYERS];
+	struct ball balls[WORLD_MAX_BULLETS];
+};
+
+int dp_snapshot_put_player(struct snapshot *, uint32_t id, const struct player *);
+struct player *dp_snapshot_get_player(struct snapshot *, uint32_t id);
+int dp_snapshot_remove_player(struct snapshot *, uint32_t id);
+int dp_snapshot_set_player_input(struct snapshot *, uint32_t id, uint8_t input);
+
+int dp_snapshot_put_ball(struct snapshot *, uint32_t id, const struct ball *);
+struct ball *dp_snapshot_get_ball(struct snapshot *, uint32_t id);
+int dp_snapshot_remove_ball(struct snapshot *, uint32_t id);
diff --git a/lib/types.h b/lib/types.h
index 8618df9..bf42576 100644
--- a/lib/types.h
+++ b/lib/types.h
@@ -1,3 +1,10 @@
+#ifndef _TYPES_H
+#define _TYPES_H
+
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+
 typedef struct {
 	float x;
 	float y;
@@ -10,3 +17,5 @@ vec2 dp_vec2_mul(vec2, float scalar);
 vec2 dp_vec2_dot(vec2, vec2);
 float dp_vec2_length(vec2);
 vec2 dp_vec2_normal(vec2);
+
+#endif
diff --git a/lib/vec2.c b/lib/vec2.c
index d795d50..55f5078 100644
--- a/lib/vec2.c
+++ b/lib/vec2.c
@@ -61,7 +61,8 @@ dp_vec2_length(vec2 v)
 vec2
 dp_vec2_normal(vec2 v)
 {
-	float a;
-	a = 1.f / dp_vec2_length(v);
-	return dp_vec2_mul(v, a);
+	float len = dp_vec2_length(v);
+	if (len == 0.0f)
+		return dp_vec2_new(0.0f, 0.0f);
+	return dp_vec2_mul(v, 1.0f / len);
 }
diff --git a/lib/world.c b/lib/world.c
deleted file mode 100644
index 34d7489..0000000
--- a/lib/world.c
+++ /dev/null
@@ -1,105 +0,0 @@
-#include <stdlib.h>
-#include <string.h>
-
-#include "types.h"
-#include "world.h"
-#include "log.h"
-
-struct world {
-	struct entity entities[WORLD_MAX_ENTITIES];
-};
-
-struct world *
-dp_world_create()
-{
-	struct world *w;
-
-	if (!(w = malloc(sizeof(*w))))
-		return NULL;
-	memset(w, 0, sizeof(*w));
-
-	return w;
-}
-
-void
-dp_free_world(struct world *w)
-{
-	if (w)
-		free(w);
-}
-
-int
-dp_world_create_entity(struct world *w, int kind)
-{
-	int i;
-	struct entity *e;
-
-	if (!w)
-		return -1;
-	if (kind == ENTITY_NONE)
-		return -1;
-	
-	for (i = 0; i < WORLD_MAX_ENTITIES; i++) {
-		e = &w->entities[i];
-		if (e->kind != ENTITY_NONE)
-			continue;
-		e->kind = kind;
-		return i;
-	}
-
-	return -1;
-}
-
-struct entity *
-dp_world_find_entity(struct world *w, int entity_id)
-{
-	struct entity *e;
-
-	if (!w || entity_id < 0)
-		return NULL;
-	if (entity_id >= WORLD_MAX_ENTITIES)
-		return NULL;
-
-	e = &w->entities[entity_id];
-	
-	if (e->kind == ENTITY_NONE)
-		return NULL;
-
-	return e;
-}
-
-int
-dp_world_remove_entity(struct world *w, int entity_id)
-{
-	struct entity *e;
-
-	if (!(e = dp_world_find_entity(w, entity_id)))
-		return -1;
-
-	memset(e, 0, sizeof(*e));
-	e->kind = ENTITY_NONE;
-	return 0;
-}
-
-int
-dp_world_tick(struct world *w, double delta)
-{
-	int i;
-	struct entity *e;
-	struct entity_ball *ball;
-	
-	for (i = 0; i < WORLD_MAX_ENTITIES; i++)
-	{
-		e = &w->entities[i];
-		switch (e->kind) {
-		case ENTITY_BALL:
-			ball = &e->e.ball;
-			/*ball->pos = dp_vec2_new(500.0, 500.0);*/
-			ball->pos = dp_vec2_add(ball->pos, dp_vec2_mul(ball->vel, delta));
-			break;
-		default:
-			break;
-		}
-	}
-	return 0;
-}
diff --git a/lib/world.h b/lib/world.h
deleted file mode 100644
index 40c3fef..0000000
--- a/lib/world.h
+++ /dev/null
@@ -1,31 +0,0 @@
-#define WORLD_MAX_ENTITIES 5000
-
-enum {
-	ENTITY_NONE,
-	ENTITY_BALL
-};
-
-struct entity_ball {
-	vec2 pos;
-	vec2 vel;
-};
-
-union entity_union {
-	struct entity_ball ball;
-};
-
-struct entity {
-	int kind;
-	union entity_union e;
-};
-
-struct world;
-
-struct world *dp_world_create();
-void dp_world_free(struct world *);
-
-int dp_world_create_entity(struct world *, int kind);
-struct entity *dp_world_find_entity(struct world *, int entity_id);
-int dp_world_remove_entity(struct world *, int entity_id);
-
-int dp_world_tick(struct world *, double delta);