diff --git a/Makefile b/Makefile
index 40382d5..a16be38 100644
--- a/Makefile
+++ b/Makefile
@@ -25,6 +25,7 @@ CFLAGS += -flto
 
 LDFLAGS =
 LDFLAGS += -lm
+LDFLAGS += -lSDL2
 
 ifdef ComSpec
 	RM = del /F /Q
diff --git a/test.c b/test.c
index 7362aa8..938f3e5 100644
--- a/test.c
+++ b/test.c
@@ -1,8 +1,19 @@
 #include "Tinn.h"
 #include <stdio.h>
+#include <stdbool.h>
 #include <time.h>
+#include <float.h>
 #include <string.h>
 #include <stdlib.h>
+#include <SDL2/SDL.h>
+
+typedef struct
+{
+    bool down;
+    int x;
+    int y;
+}
+Input;
 
 typedef struct
 {
@@ -125,6 +136,93 @@ static Data build(const char* path, const int nips, const int nops)
     return data;
 }
 
+void dprint(const float* const p, const int size)
+{
+    for(int i = 0; i < size; i++)
+        printf("%f ", (double) p[i]);
+    printf("\n");
+}
+
+typedef struct
+{
+    int i;
+    float val;
+}
+Index;
+
+Index ixmax(const float* const p, const int size)
+{
+    Index ix;
+    ix.val = -FLT_MAX;
+    for(int i = 0; i < size; i++)
+        if(p[i] > ix.val)
+            ix.val = p[ix.i = i];
+    return ix;
+}
+
+void dploop(const Tinn tinn, const Data data)
+{
+    SDL_Renderer* renderer;
+    SDL_Window* window;
+    #define W 16
+    #define H 16
+    #define S 20
+    const int xres = W * S;
+    const int yres = H * S;
+    SDL_CreateWindowAndRenderer(xres, yres, 0, &window, &renderer);
+    static float digit[W * H];
+    Input input = { false, 0, 0 };
+    for(SDL_Event e; true; SDL_PollEvent(&e))
+    {
+        if(e.type == SDL_QUIT)
+            exit(1);
+        const int button = SDL_GetMouseState(&input.x, &input.y);
+        // Draw digit.
+        if(button)
+        {
+            const int xx = input.x / S;
+            const int yy = input.y / S;
+            const int w = 2;
+            for(int i = 0; i < w; i++)
+            for(int j = 0; j < w; j++)
+                digit[(xx + i) + W * (yy + j)] = 1.0f;
+            input.down = true;
+        }
+        // Predict.
+        else
+        {
+            if(input.down)
+            {
+                const float* const pred = xpredict(tinn, digit);
+                dprint(pred, data.nops);
+                const Index ix = ixmax(pred, data.nops);
+                if(ix.val > 0.9f)
+                    printf("%d\n", ix.i);
+                else
+                    printf("I do not recognize that digit\n");
+                memset((void*) digit, 0, sizeof(digit));
+            }
+            input.down = false;
+        }
+        // Draw digit to screen.
+        for(int x = 0; x < xres; x++)
+        for(int y = 0; y < yres; y++)
+        {
+            const int xx = x / S;
+            const int yy = y / S;
+            digit[xx + W * yy] == 1.0f ?
+                SDL_SetRenderDrawColor(renderer, 0xFF, 0xFF, 0xFF, 0xFF):
+                SDL_SetRenderDrawColor(renderer, 0x00, 0x00, 0x00, 0xFF);
+            SDL_RenderDrawPoint(renderer, x, y);
+        }
+        SDL_RenderPresent(renderer);
+        SDL_Delay(15);
+    }
+    #undef W
+    #undef H
+    #undef S
+}
+
 int main()
 {
     // Tinn does not seed the random number generator.
@@ -144,7 +242,7 @@ int main()
     const Data data = build("semeion.data", nips, nops);
     // Train, baby, train.
     const Tinn tinn = xtbuild(nips, nhid, nops);
-    for(int i = 0; i < 100; i++)
+    for(int i = 0; i < 200; i++)
     {
         shuffle(data);
         float error = 0.0f;
@@ -163,14 +261,10 @@ int main()
     // This is how you load the neural network from disk.
     const Tinn loaded = xtload("saved.tinn");
     // Now we do a prediction with the neural network we loaded from disk.
-    // Ideally, we would also load a testing set to make the prediction with,
-    // but for the sake of brevity here we just reuse the training set from earlier.
-    const float* const in = data.in[0];
-    const float* const tg = data.tg[0];
-    const float* const pd = xpredict(loaded, in);
-    for(int i = 0; i < data.nops; i++) { printf("%f ", (double) tg[i]); } printf("\n");
-    for(int i = 0; i < data.nops; i++) { printf("%f ", (double) pd[i]); } printf("\n");
-    // All done. Let's clean up.
+    // SDL will create a window so that you can draw digits.
+    // Enter the draw and predict loop:
+    dploop(loaded, data);
+    // All done. Let's clean up
     xtfree(loaded);
     dfree(data);
     return 0;