diff --git a/base/backtrace.cpp b/base/backtrace.cpp
new file mode 100644
index 0000000000..422b1e17b8
--- /dev/null
+++ b/base/backtrace.cpp
@@ -0,0 +1,17 @@
+#include "base/backtrace.h"
+
+#ifndef _MSC_VER
+
+// LINUX ONLY
+
+#include <execinfo.h>
+#include <unistd.h>
+
+static void *backtrace_buffer[128];
+
+void PrintBacktraceToStderr() {
+  int num_addrs = backtrace(backtrace_buffer, 128);
+  backtrace_symbols_fd(backtrace_buffer, num_addrs, STDERR_FILENO);
+}
+
+#endif
\ No newline at end of file
diff --git a/base/backtrace.h b/base/backtrace.h
new file mode 100644
index 0000000000..4ff0917f30
--- /dev/null
+++ b/base/backtrace.h
@@ -0,0 +1,3 @@
+#pragma once
+
+void PrintBacktraceToStderr();
diff --git a/base/fastlist.h b/base/fastlist.h
new file mode 100644
index 0000000000..78ba4e5512
--- /dev/null
+++ b/base/fastlist.h
@@ -0,0 +1,37 @@
+#pragma once
+
+// An inline fastlist is a fixed size array with a position counter.
+// Objects stored in a fastlist must be copyable.
+// [] returns the objects in consecutive order, up to and not including
+// the value of .size().
+// Order is not preserved when removing objects.
+template<class T, int max_size>
+class InlineFastList {
+ public:
+  InlineFastList() : count_(0) {}
+  ~InlineFastList() {}
+
+  T& operator [](int index) { return data_[index]; }
+  const T& operator [](int index) const { return data_[index]; }
+  int size() const { return count_; }
+  
+  void Add(T t) {
+    data_[count_++] = t;
+  }
+  void RemoveAt(int index) {
+    data_[index] = data_[count_ - 1];
+    count_--;
+  }
+  void Remove(T t) {  // Requires operator==
+    for (int i = 0; i < count_; i++) {
+      if (data_[i] == t) {
+        RemoveAt(i);
+        return;
+      }
+    }
+  }
+
+ private:
+  T data_[max_size];
+  int count_;
+};
diff --git a/base/fastlist_test.cpp b/base/fastlist_test.cpp
new file mode 100644
index 0000000000..57064adcc4
--- /dev/null
+++ b/base/fastlist_test.cpp
@@ -0,0 +1,19 @@
+#include "base/fastlist.h"
+#include "base/logging.h"
+
+/*
+#include <gtest/gtest.h>
+
+TEST(fastlist, AddRemove) {
+  InlineFastList<int, 8> list;
+  list.Add(8);
+  list.Remove(7);
+  EXPECT_EQ(1, list.size());
+  list.Remove(8);
+  EXPECT_EQ(0, list.size());
+  list.Add(1);
+  list.Add(2);
+  list.Add(3);
+  EXPECT_EQ(3, list.size());
+}
+*/
\ No newline at end of file
diff --git a/base/linked_ptr.h b/base/linked_ptr.h
new file mode 100644
index 0000000000..4be7c3ddab
--- /dev/null
+++ b/base/linked_ptr.h
@@ -0,0 +1,113 @@
+// From http://ootips.org/yonat/4dev/linked_ptr.h
+
+/*
+ * linked_ptr - simple reference linked pointer
+ * (like reference counting, just using a linked list of the references
+ * instead of their count.)
+ *
+ * The implementation stores three pointers for every linked_ptr, but
+ * does not allocate anything on the free store.
+ */
+
+#pragma once
+
+/* For ANSI-challenged compilers, you may want to #define
+ * NO_MEMBER_TEMPLATES, explicit or mutable */
+
+#ifdef _MSC_VER
+#define NO_MEMBER_TEMPLATES
+#endif
+
+template <class X> class linked_ptr
+{
+public:
+
+#ifndef NO_MEMBER_TEMPLATES
+#   define TEMPLATE_FUNCTION template <class Y>
+    TEMPLATE_FUNCTION friend class linked_ptr<Y>;
+#else
+#   define TEMPLATE_FUNCTION
+    typedef X Y;
+#endif
+
+    typedef X element_type;
+
+    explicit linked_ptr(X* p = 0) throw()
+        : itsPtr(p) {itsPrev = itsNext = this;}
+    ~linked_ptr()
+        {release();}
+    linked_ptr(const linked_ptr& r) throw()
+        {acquire(r);}
+    linked_ptr& operator=(const linked_ptr& r)
+    {
+        if (this != &r) {
+            release();
+            acquire(r);
+        }
+        return *this;
+    }
+
+#ifndef NO_MEMBER_TEMPLATES
+    template <class Y> friend class linked_ptr<Y>;
+    template <class Y> linked_ptr(const linked_ptr<Y>& r) throw()
+        {acquire(r);}
+    template <class Y> linked_ptr& operator=(const linked_ptr<Y>& r)
+    {
+        if (this != &r) {
+            release();
+            acquire(r);
+        }
+        return *this;
+    }
+#endif // NO_MEMBER_TEMPLATES
+
+    X& operator*()  const throw()   {return *itsPtr;}
+    X* operator->() const throw()   {return itsPtr;}
+    X* get()        const throw()   {return itsPtr;}
+    bool unique()   const throw()   {return itsPrev ? itsPrev==this : true;}
+
+private:
+    X*                          itsPtr;
+    mutable const linked_ptr*   itsPrev;
+    mutable const linked_ptr*   itsNext;
+
+    void acquire(const linked_ptr& r) throw()
+    { // insert this to the list
+        itsPtr = r.itsPtr;
+        itsNext = r.itsNext;
+        itsNext->itsPrev = this;
+        itsPrev = &r;
+#ifndef mutable
+        r.itsNext = this;
+#else // for ANSI-challenged compilers
+        (const_cast<linked_ptr<X>*>(&r))->itsNext = this;
+#endif
+    }
+
+#ifndef NO_MEMBER_TEMPLATES
+    template <class Y> void acquire(const linked_ptr<Y>& r) throw()
+    { // insert this to the list
+        itsPtr = r.itsPtr;
+        itsNext = r.itsNext;
+        itsNext->itsPrev = this;
+        itsPrev = &r;
+#ifndef mutable
+        r.itsNext = this;
+#else // for ANSI-challenged compilers
+        (const_cast<linked_ptr<X>*>(&r))->itsNext = this;
+#endif
+    }
+#endif // NO_MEMBER_TEMPLATES
+
+    void release()
+    { // erase this from the list, delete if unique
+        if (unique()) delete itsPtr;
+        else {
+            itsPrev->itsNext = itsNext;
+            itsNext->itsPrev = itsPrev;
+            itsPrev = itsNext = 0;
+        }
+        itsPtr = 0;
+    }
+};
+
diff --git a/math/lin/aabb.cpp b/math/lin/aabb.cpp
index 4e73b512a0..6a04ddab14 100644
--- a/math/lin/aabb.cpp
+++ b/math/lin/aabb.cpp
@@ -7,8 +7,6 @@
 #define LEFT	1
 #define MIDDLE	2
 
-namespace lin {
-
 static const float flt_plus_inf = -logf(0);	// let's keep C and C++ compilers happy.
 
 AABB::AABB() : minB(0,0,0),maxB(0,0,0) {
@@ -268,5 +266,3 @@ bool AABB::BehindPlane(const Plane &plane) const {
 
   return true;
 }
-
-}  // namespace lin
diff --git a/math/lin/aabb.h b/math/lin/aabb.h
index 22f2a7b80d..6f887f876e 100644
--- a/math/lin/aabb.h
+++ b/math/lin/aabb.h
@@ -1,11 +1,8 @@
-#ifndef _MATH_LIN_AABB
-#define _MATH_LIN_AABB
+#pragma once
 
 #include "math/lin/vec3.h"
 
-namespace lin {
-
-class Ray;
+struct Ray;
 class Plane;
 
 struct AABB {
@@ -41,7 +38,3 @@ struct AABB {
 
   bool BehindPlane(const Plane &plane) const;
 };
-
-}  // namespace lin
-
-#endif  // _MATH_LIN_AABB
diff --git a/math/lin/plane.cpp b/math/lin/plane.cpp
index 31b52fa00d..67e8ef631a 100644
--- a/math/lin/plane.cpp
+++ b/math/lin/plane.cpp
@@ -1,13 +1,10 @@
 #include "math/lin/matrix4x4.h"
 #include "math/lin/plane.h"
 
-namespace lin {
 
-Plane Plane::TransformByIT(const Matrix4x4 &m, Plane *out) {
+void Plane::TransformByIT(const Matrix4x4 &m, Plane *out) {
   out->x = x * m.xx + y * m.yx + z * m.zx + d * m.wx;
   out->y = x * m.xy + y * m.yy + z * m.zy + d * m.wy;
   out->z = x * m.xz + y * m.yz + z * m.zz + d * m.wz;
   out->d = x * m.xw + y * m.yw + z * m.zw + d * m.ww;
 }
-
-}
diff --git a/math/lin/plane.h b/math/lin/plane.h
index 02c7ad22da..6466617c1b 100644
--- a/math/lin/plane.h
+++ b/math/lin/plane.h
@@ -3,8 +3,6 @@
 
 #include "math/lin/vec3.h"
 
-namespace lin {
-
 class Matrix4x4;
 
 class Plane {
@@ -24,7 +22,7 @@ class Plane {
   }
 
   void Normalize() {
-    float inv_length = 1.0 * sqrtf(x * x + y * y + z * z);
+    float inv_length = sqrtf(x * x + y * y + z * z);
     x *= inv_length;
     y *= inv_length;
     z *= inv_length;
@@ -33,9 +31,7 @@ class Plane {
 
   // Matrix is the inverse transpose of the wanted transform.
   // out cannot be equal to this.
-  Plane TransformByIT(const Matrix4x4 &matrix, Plane *out);
+  void TransformByIT(const Matrix4x4 &matrix, Plane *out);
 };
 
-}
-
 #endif
diff --git a/math/lin/ray.h b/math/lin/ray.h
index 5c9a5e91e0..2287460fbb 100644
--- a/math/lin/ray.h
+++ b/math/lin/ray.h
@@ -1,10 +1,7 @@
-#ifndef _MATH_LIN_RAY_H
-#define _MATH_LIN_RAY_H
+#pragma once
 
 #include "vec3.h"
 
-namespace lin {
-
 /* __declspec(align(16)) */ struct Ray
 {
 	Vec3 origin;
@@ -15,6 +12,3 @@ namespace lin {
 	int pad3;
 };
 
-}  // namespace lin
-
-#endif  // _MATH_LIN_RAY_H
diff --git a/math/lin/vec3.h b/math/lin/vec3.h
index 5355f20977..e10fc0d3a9 100644
--- a/math/lin/vec3.h
+++ b/math/lin/vec3.h
@@ -22,6 +22,9 @@ public:
   Vec3() { }
   explicit Vec3(float f) {x=y=z=f;}
 
+  float operator [] (int i) const { return (&x)[i]; }
+  float &operator [] (int i) { return (&x)[i]; }
+
   Vec3(const float _x, const float _y, const float _z) {
     x=_x; y=_y; z=_z;
   }
diff --git a/math/math_util.h b/math/math_util.h
index b6196f8240..71edd44a0b 100644
--- a/math/math_util.h
+++ b/math/math_util.h
@@ -1,8 +1,8 @@
 #ifndef _MATHUTILS_H
 #define _MATHUTILS_H
 
-#include <math.h>
-#include <string.h>
+#include <cmath>
+#include <cstring>
 
 inline float sqr(float f)  {return f*f;}
 inline float sqr_signed(float f) {return f<0 ? -f*f : f*f;}
@@ -26,6 +26,9 @@ inline float Float16ToFloat(float16 ix) {
 
 
 #define PI 3.141592653589793f
+#ifndef M_PI
+#define M_PI 3.141592653589793f
+#endif
 
 // The stuff in this file is from all over the web, esp. dspmusic.org. I think it's all public domain.
 // In any case, very little of it is used anywhere at the moment.
diff --git a/native.vcxproj b/native.vcxproj
index 909604b212..470181302e 100644
--- a/native.vcxproj
+++ b/native.vcxproj
@@ -97,12 +97,15 @@
     <ClInclude Include="android\native_audio.h" />
     <ClInclude Include="audio\mixer.h" />
     <ClInclude Include="audio\wav_read.h" />
+    <ClInclude Include="base\backtrace.h" />
     <ClInclude Include="base\basictypes.h" />
     <ClInclude Include="base\buffer.h" />
     <ClInclude Include="base\color.h" />
     <ClInclude Include="base\colorutil.h" />
     <ClInclude Include="base\display.h" />
     <ClInclude Include="base\error_context.h" />
+    <ClInclude Include="base\fastlist.h" />
+    <ClInclude Include="base\linked_ptr.h" />
     <ClInclude Include="base\logging.h" />
     <ClInclude Include="base\mutex.h" />
     <ClInclude Include="base\NativeApp.h" />
@@ -140,7 +143,9 @@
     <ClInclude Include="input\input_state.h" />
     <ClInclude Include="json\json_writer.h" />
     <ClInclude Include="math\compression.h" />
+    <ClInclude Include="math\lin\aabb.h" />
     <ClInclude Include="math\lin\matrix4x4.h" />
+    <ClInclude Include="math\lin\plane.h" />
     <ClInclude Include="math\lin\quat.h" />
     <ClInclude Include="math\lin\vec3.h" />
     <ClInclude Include="math\math_util.h" />
@@ -148,9 +153,12 @@
     <ClInclude Include="net\http_client.h" />
     <ClInclude Include="net\resolve.h" />
     <ClInclude Include="profiler\profiler.h" />
+    <ClInclude Include="ui\list_screen.h" />
     <ClInclude Include="ui\screen.h" />
     <ClInclude Include="ui\ui.h" />
     <ClInclude Include="util\bits\bits.h" />
+    <ClInclude Include="util\random\perlin.h" />
+    <ClInclude Include="util\random\rng.h" />
   </ItemGroup>
   <ItemGroup>
     <ClCompile Include="android\app-android.cpp">
@@ -167,6 +175,7 @@
     </ClCompile>
     <ClCompile Include="audio\mixer.cpp" />
     <ClCompile Include="audio\wav_read.cpp" />
+    <ClCompile Include="base\backtrace.cpp" />
     <ClCompile Include="base\buffer.cpp" />
     <ClCompile Include="base\colorutil.cpp" />
     <ClCompile Include="base\display.cpp" />
@@ -203,7 +212,9 @@
     <ClCompile Include="image\zim_save.cpp" />
     <ClCompile Include="input\gesture_detector.cpp" />
     <ClCompile Include="json\json_writer.cpp" />
+    <ClCompile Include="math\lin\aabb.cpp" />
     <ClCompile Include="math\lin\matrix4x4.cpp" />
+    <ClCompile Include="math\lin\plane.cpp" />
     <ClCompile Include="math\lin\quat.cpp" />
     <ClCompile Include="math\lin\vec3.cpp" />
     <ClCompile Include="math\math_util.cpp" />
@@ -211,9 +222,11 @@
     <ClCompile Include="net\http_client.cpp" />
     <ClCompile Include="net\resolve.cpp" />
     <ClCompile Include="profiler\profiler.cpp" />
+    <ClCompile Include="ui\list_screen.cpp" />
     <ClCompile Include="ui\screen.cpp" />
     <ClCompile Include="ui\ui.cpp" />
     <ClCompile Include="util\bits\bits.cpp" />
+    <ClCompile Include="util\random\perlin.cpp" />
   </ItemGroup>
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
   <ImportGroup Label="ExtensionTargets">
diff --git a/native.vcxproj.filters b/native.vcxproj.filters
index e23e6418a1..a9609633e4 100644
--- a/native.vcxproj.filters
+++ b/native.vcxproj.filters
@@ -184,6 +184,30 @@
     <ClInclude Include="ui\screen.h">
       <Filter>ui</Filter>
     </ClInclude>
+    <ClInclude Include="base\linked_ptr.h">
+      <Filter>base</Filter>
+    </ClInclude>
+    <ClInclude Include="ui\list_screen.h">
+      <Filter>ui</Filter>
+    </ClInclude>
+    <ClInclude Include="base\backtrace.h">
+      <Filter>base</Filter>
+    </ClInclude>
+    <ClInclude Include="base\fastlist.h">
+      <Filter>base</Filter>
+    </ClInclude>
+    <ClInclude Include="math\lin\aabb.h">
+      <Filter>math</Filter>
+    </ClInclude>
+    <ClInclude Include="math\lin\plane.h">
+      <Filter>math</Filter>
+    </ClInclude>
+    <ClInclude Include="util\random\perlin.h">
+      <Filter>util</Filter>
+    </ClInclude>
+    <ClInclude Include="util\random\rng.h">
+      <Filter>util</Filter>
+    </ClInclude>
   </ItemGroup>
   <ItemGroup>
     <ClCompile Include="gfx\gl_debug_log.cpp">
@@ -333,6 +357,21 @@
     <ClCompile Include="ui\screen.cpp">
       <Filter>ui</Filter>
     </ClCompile>
+    <ClCompile Include="ui\list_screen.cpp">
+      <Filter>ui</Filter>
+    </ClCompile>
+    <ClCompile Include="base\backtrace.cpp">
+      <Filter>base</Filter>
+    </ClCompile>
+    <ClCompile Include="math\lin\aabb.cpp">
+      <Filter>math</Filter>
+    </ClCompile>
+    <ClCompile Include="math\lin\plane.cpp">
+      <Filter>math</Filter>
+    </ClCompile>
+    <ClCompile Include="util\random\perlin.cpp">
+      <Filter>util</Filter>
+    </ClCompile>
   </ItemGroup>
   <ItemGroup>
     <Filter Include="gfx">
diff --git a/ui/list_screen.cpp b/ui/list_screen.cpp
new file mode 100644
index 0000000000..c3cedcd59b
--- /dev/null
+++ b/ui/list_screen.cpp
@@ -0,0 +1,6 @@
+#include "ui/list_screen.h"
+
+ListScreen::ListScreen() {
+
+}
+
diff --git a/ui/list_screen.h b/ui/list_screen.h
new file mode 100644
index 0000000000..9dc08f17e2
--- /dev/null
+++ b/ui/list_screen.h
@@ -0,0 +1,10 @@
+#include "ui/screen.h"
+
+
+class ListScreen {
+public:
+  ListScreen();
+  
+private:
+
+};
\ No newline at end of file
diff --git a/ui/screen.h b/ui/screen.h
index cb168ec1d2..e2637599ff 100644
--- a/ui/screen.h
+++ b/ui/screen.h
@@ -56,7 +56,7 @@ private:
 	Screen *currentScreen_;
 	Screen *nextScreen_;
 
-  // Dialog stack. These are shown "on top" of base screens and back works as expected.
+  // Dialog stack. These are shown "on top" of base screens and the Android back button works as expected.
   // Used for options, in-game menus and other things you expect to be able to back out from onto something.
   std::list<Screen *> dialog_;
 };
diff --git a/ui/ui.cpp b/ui/ui.cpp
index b4bda255a5..d6a0df757d 100644
--- a/ui/ui.cpp
+++ b/ui/ui.cpp
@@ -10,6 +10,8 @@
 // TODO: UI should probably not own these.
 DrawBuffer ui_draw2d;
 DrawBuffer ui_draw2d_front;
+
+// This one, though, is OK.
 UIState uistate;
 
 // Theme.
diff --git a/ui/ui.h b/ui/ui.h
index 2849ff5690..78c16da1b5 100644
--- a/ui/ui.h
+++ b/ui/ui.h
@@ -5,6 +5,10 @@
 // A common pattern is Adapter classes for changing how things are drawn
 // in lists, for example.
 //
+// Immediate UI works great for overlay UI for games, for example, but is actually
+// not really a good idea for full app UIs. Also, animations are difficult because
+// there's not really any good place to store state.
+//
 // hrydgard@gmail.com
 
 #pragma once
diff --git a/util/random/perlin.cpp b/util/random/perlin.cpp
index d0ee8a9fa4..e8a8a578df 100644
--- a/util/random/perlin.cpp
+++ b/util/random/perlin.cpp
@@ -47,14 +47,14 @@ inline float grad(int hash, float x, float y, float z) {
   return ((h & 1) == 0 ? u : -u) + ((h & 2) == 0 ? v : -v);
 }
 
-float Noise(double z, double y, double x) {
-  double fx = floor(x), fy = floor(y), fz = floor(z);
+float Noise(double iz, double iy, double ix) {
+  double fx = floor(ix), fy = floor(iy), fz = floor(iz);
   int X = (int)fx & 255,                  // FIND UNIT CUBE THAT
       Y = (int)fy & 255,                  // CONTAINS POINT.
       Z = (int)fz & 255;
-  x -= fx;                                // FIND RELATIVE X,Y,Z
-  y -= fy;                                // OF POINT IN CUBE.
-  z -= fz;
+  float x = (float)(ix - fx);                                // FIND RELATIVE X,Y,Z
+  float y = (float)(iy - fy);                                // OF POINT IN CUBE.
+  float z = (float)(iz - fz);
   float u = fade(x);                           // COMPUTE FADE CURVES
   float v = fade(y);                           // FOR EACH OF X,Y,Z.
   float w = fade(z);
diff --git a/util/random/perlin.h b/util/random/perlin.h
index ace8c521d3..ecda001c23 100644
--- a/util/random/perlin.h
+++ b/util/random/perlin.h
@@ -1,8 +1,6 @@
-#ifndef _PERLIN_H
-#define _PERLIN_H
+#pragma once
 
 // Implementation of "Improved Noise"
 // http://mrl.nyu.edu/~perlin/noise/ 
+// doubles are only used at the very start, not a big performance worry
 float Noise(double x, double y, double z);
-
-#endif  // _PERLIN_H
diff --git a/util/random/rng.h b/util/random/rng.h
index 28369196a6..68e66d79b9 100644
--- a/util/random/rng.h
+++ b/util/random/rng.h
@@ -1,5 +1,4 @@
-#ifndef _RNG_H
-#define _RNG_H
+#pragma once
 
 #include "base/basictypes.h"
 
@@ -22,5 +21,3 @@ class GMRng {
   uint32 m_w;
   uint32 m_z;
 };
-
-#endif