diff --git a/mono/Assistance/InputState.cs b/mono/Assistance/InputState.cs
new file mode 100644
index 0000000..81560cd
--- /dev/null
+++ b/mono/Assistance/InputState.cs
@@ -0,0 +1,119 @@
+using System;
+using System.Collections.Generic;
+
+namespace Assistance {
+	public class InputState {
+		public long ticks;
+		public KeyHistory<Gdk.Key> keyHistory = new KeyHistory<Gdk.Key>();
+		public readonly Dictionary<Gdk.Device, KeyHistory<uint>> buttonHistories = new Dictionary<Gdk.Device, KeyHistory<uint>>();
+		
+		public void touch(long ticks) {
+			if (this.ticks < ticks)
+				this.ticks = ticks;
+			else
+				++this.ticks;
+		}
+		
+		public KeyState<Gdk.Key> keyState
+			{ get { return keyHistory.current; } }
+		
+		public void keyEvent(bool press, Gdk.Key key, long ticks) {
+			touch(ticks);
+			keyHistory.change(press, key, this.ticks);
+		}
+		public void keyPress(Gdk.Key key, long ticks)
+			{ keyEvent(true, key, ticks); }
+		public void keyRelease(Gdk.Key key, long ticks)
+			{ keyEvent(false, key, ticks); }
+		
+		public KeyState<Gdk.Key> keyFind(Gdk.Key key)
+			{ return keyState.find(key); }
+		public bool isKeyPressed(Gdk.Key key)
+			{ return keyFind(key) != null; }
+		public double howLongKeyPressed(Gdk.Key key, long ticks, double timeOffset = 0.0)
+			{ return KeyState<Gdk.Key>.Holder.howLongPressed(keyFind(key), ticks, timeOffset); }
+		public double howLongKeyPressed(Gdk.Key key)
+			{ return howLongKeyPressed(key, ticks); }
+
+		public KeyHistory<uint> buttonHistory(Gdk.Device device) {
+			KeyHistory<uint> history;
+			if (!buttonHistories.TryGetValue(device, out history))
+				history = new KeyHistory<uint>();
+				buttonHistories[device] = history;
+			return history;
+		}
+		public KeyState<uint> buttonState(Gdk.Device device)
+			{ buttonHistory(device).current; }
+
+		public void buttonEvent(bool press, Gdk.Device device, uint button, long ticks) {
+			touch(ticks);
+			buttonHistory(device).change(press, button, this.ticks);
+		}
+		public void buttonPress(Gdk.Device device, uint button, long ticks)
+			{ buttonEvent(true, device, button, ticks); }
+		public void buttonRelease(Gdk.Device device, uint button, long ticks)
+			{ buttonEvent(false, device, button, ticks); }
+		public void buttonEvent(bool press, uint button, long ticks)
+			{ buttonEvent(press, null, button, ticks); }
+		public void buttonPress(uint button, long ticks)
+			{ buttonEvent(true, button, ticks); }
+		public void buttonRelease(uint button, long ticks)
+			{ buttonEvent(false, button, ticks); }
+
+		public KeyState<uint> buttonFind(Gdk.Device device, uint button)
+			{ return buttonState(device).find(button); }
+		public bool isButtonPressed(Gdk.Device device, uint button)
+			{ return buttonFind(device, button) != null; }
+		public double howLongButtonPressed(Gdk.Device device, uint button, long ticks, double timeOffset = 0.0)
+			{ return KeyState<uint>.Holder.howLongPressed(buttonFind(device, button), ticks, timeOffset); }
+		public double howLongButtonPressed(Gdk.Device device, uint button)
+			{ return howLongButtonPressed(device, ticks); }
+
+		public KeyState<uint> buttonFindDefault(uint button)
+			{ return buttonFind(null, button); }
+		public bool isButtonPressedDefault(uint button)
+			{ return isButtonPressed(null, button); }
+		public double howLongButtonPressedDefault(uint button, long ticks, double timeOffset = 0.0)
+			{ return howLongButtonPressed(null, button, ticks, timeOffset); }
+		public double howLongButtonPressedDefault(uint button)
+			{ return howLongButtonPressedDefault(button, ticks); }
+
+		public KeyState<uint> buttonFindAny(uint button, out Gdk.Device device) {
+			device = null;
+			KeyState<uint> state = null;
+			foreach(KeyValuePair<Gdk.Device, KeyHistory<uint>> pair in buttonHistories) {
+				KeyState<uint> s = pair.Value == null ? null : pair.Value.current.find(button);
+				if (s != null && (state == null || s.ticks < state.ticks))
+					{ state = s; device = pair.Key; }
+			}
+			return state;
+		}
+		public KeyState<uint> buttonFindAny(uint button)
+			{ Gdk.Device device; return buttonFindAny(button, out device); }
+		public bool isButtonPressedAny(uint button)
+			{ return buttonFindAny(button) != null; }
+		public double howLongButtonPressedAny(uint button, long ticks, double timeOffset = 0.0)
+			{ return KeyState<uint>.Holder.howLongPressed(buttonFindAny(button), ticks, timeOffset); }
+		public double howLongButtonPressedAny(uint button)
+			{ return howLongButtonPressedAny(button, ticks); }
+
+		public KeyState<Gdk.Key>.Holder keyStateHolder(long ticks, double timeOffset = 0.0)
+			{ return new KeyState<Gdk.Key>.Holder(keyState, ticks, timeOffset); }
+		public KeyState<Gdk.Key>.Holder keyStateHolder()
+			{ return keyStateHolder(ticks); }
+		public KeyHistory<Gdk.Key>.Holder keyStateHolder(long ticks, double timeOffset = 0.0)
+			{ return new KeyHistory<Gdk.Key>.Holder(keyHistory, ticks, timeOffset); }
+		public KeyHistory<Gdk.Key>.Holder keyStateHolder()
+			{ return keyStateHolder(ticks); }
+
+		public KeyState<uint>.Holder buttonStateHolder(Gdk.Device device, long ticks, double timeOffset = 0.0)
+			{ return new KeyState<uint>.Holder(buttonState(device), ticks, timeOffset); }
+		public KeyState<uint>.Holder buttonStateHolder(Gdk.Device device)
+			{ return buttonStateHolder(device, ticks); }
+		public KeyHistory<uint>.Holder buttonHistoryHolder(Gdk.Device device, long ticks, double timeOffset = 0.0)
+			{ return new KeyHistory<uint>.Holder(buttonHistory(device), ticks, timeOffset); }
+		public KeyHistory<uint>.Holder buttonHistoryHolder(Gdk.Device device)
+			{ return buttonHistoryHolder(buttonHistory(device), ticks); }
+	}
+}
+
diff --git a/mono/Assistance/KeyHistory.cs b/mono/Assistance/KeyHistory.cs
new file mode 100644
index 0000000..ea3fdaf
--- /dev/null
+++ b/mono/Assistance/KeyHistory.cs
@@ -0,0 +1,104 @@
+using System;
+using System.Collections.Generic;
+
+namespace Assistance {
+	public class KeyHistory<T> where T: IComparable, new() {
+		public class Holder: IDisposable {
+			public readonly KeyHistory<T> history;
+			public readonly long ticks;
+			public readonly double timeOffset;
+
+			private readonly long heldTicks;
+			private bool disposed = false;
+
+			public Holder(KeyHistory<T> history, long ticks, double timeOffset = 0.0) {
+				this.history = history;
+				this.ticks = ticks;
+				this.timeOffset = timeOffset;
+				heldTicks = history.hold(ticks);
+			}
+			
+			public KeyState<T>.Holder get(double time) {
+				long dticks = (long)Math.Ceiling(Timer.frequency*(time + timeOffset));
+				KeyState<T> state = history.get(ticks + dticks);
+				return new KeyState<T>.Holder(state, ticks, timeOffset + time);
+			}
+
+			public void Dispose() { 
+				Dispose(true);
+				GC.SuppressFinalize(this);           
+			}
+			
+			protected virtual void Dispose(bool disposing) {
+				if (disposed) return;
+				history.release(heldTicks);
+				disposed = true;
+			}
+			
+			~Holder()
+				{ Dispose(false); }
+		}
+	
+		private readonly List<KeyState<T>> states = new List<KeyState<T>>() { new KeyState<T>() };
+		private readonly List<long> locks = new List<long>();
+		
+		public KeyState<T> current
+			{ get { return states[ states.Count - 1 ]; } }
+		
+		public void change(bool press, T value, long ticks)	{
+			states.Add(current.change(press, value, ticks));
+			autoRemove();
+		}
+		public KeyState<T> press(T value, long ticks)
+			{ return change(true, value, ticks); }
+		public KeyState<T> release(T value, long ticks)
+			{ return change(false, value, ticks); }
+		
+		private int findLock(long ticks) {
+			// locks[a] <= ticks < locks[b]
+			int a = 0;
+			int b = states.Count - 1;
+			if (locks[a] < locks) return -1;
+			if (ticks >= locks[b]) return b;
+			while(True) {
+				int c = (a + b)/2;
+				if (a == c) break;
+				if (ticks < locks[c]) b = c; else a = c;
+			}
+			return a;
+		}
+		
+		private void autoRemove() {
+			long ticks = locks.Count > 0 ? locks[0] : long.MaxValue;
+			while(states.Count > 1 && (states[0].ticks < ticks || states[0].isEmpty))
+				states.RemoveAt(0);
+		}
+		
+		private long hold(long ticks) {
+			long heldTicks = Math.Max(ticks, current.ticks);
+			locks.Insert(findLock(heldTicks) + 1, heldTicks);
+			return heldTicks;
+		}
+		
+		private void release(long heldTicks) {
+			int i = findLock(heldTicks);
+			if (i >= 0 && locks[i] == heldTicks) locks.RemoveAt(i);
+			autoRemove();
+		}
+		
+		private KeyState<T> get(long ticks) {
+			// state[a].ticks <= ticks < state[b].ticks 
+			int a = 0;
+			int b = states.Count - 1;
+			if (states[a].ticks < ticks) return new KeyState<T>();
+			if (ticks >= states[b].ticks) return states[b].ticks;
+			while(True) {
+				int c = (a + b)/2;
+				if (a == c) break;
+				if (ticks < states[c].ticks) b = c; else a = c;
+			}
+			return states[a];
+		}
+	}
+}
+
diff --git a/mono/Assistance/KeyState.cs b/mono/Assistance/KeyState.cs
index 7b46c9f..ac40ae7 100644
--- a/mono/Assistance/KeyState.cs
+++ b/mono/Assistance/KeyState.cs
@@ -27,7 +27,7 @@ namespace Assistance {
 				     : Math.Max(Timer.step, (ticks - state.ticks)*Timer.step + timeOffset);
 			}
 		}
-	
+		
 		public static readonly T none = new T();
 		public static readonly KeyState<T> empty = new KeyState<T>();