diff --git a/11/11-1and2.c b/11/11-1and2.c
new file mode 100644
index 0000000..fbe6cd5
--- /dev/null
+++ b/11/11-1and2.c
@@ -0,0 +1,156 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include <stdbool.h>
+#include "../check_alloc.h"
+
+#define PART_2
+
+typedef struct
+{
+    u_int8_t energy;
+    bool lock; // LOCK STATE WHEN GLOWING
+} OCTOPUS;
+
+//
+
+#define SPACE_SIZE 10
+
+typedef OCTOPUS **SPACE;
+
+#define VALID_VECTOR(i, j) ((i) >= 0 && (j) >= 0 && (i) < (SPACE_SIZE) && (j) < (SPACE_SIZE))
+#define ITER_SPACE(i, j)                       \
+    for (int i = 0; (i) < (SPACE_SIZE); (i)++) \
+        for (int j = 0; (j) < (SPACE_SIZE); (j)++)
+#define ITER_ADJACENT(i, j, x, y)                      \
+    for (int x = ((i)-1); (x) <= ((i) + 1); (x)++)     \
+        for (int y = ((j)-1); (y) <= ((j) + 1); (y)++) \
+            if (((x) != (i) || (y) != (j)) && VALID_VECTOR((x), (y)))
+
+bool check_sync(SPACE space)
+{
+    ITER_SPACE(i, j)
+    {
+        if (space[i][j].energy != 0)
+            return false;
+    }
+    return true;
+}
+
+size_t flash(SPACE space)
+{
+    size_t n_flashes = 0;
+    do // This can be further optimized with a update cache.
+    {
+        n_flashes = 0;
+        ITER_SPACE(i, j)
+        {
+            if (space[i][j].energy > 9)
+            {
+                ITER_ADJACENT(i, j, x, y)
+                {
+                    OCTOPUS *p_cell = &space[x][y];
+                    if (p_cell->energy > 9)
+                    {
+                        p_cell->lock = true;
+                    }
+                    else if (!p_cell->lock)
+                    {
+                        p_cell->energy++;
+                        if (p_cell->energy > 9)
+                            n_flashes++;
+                    }
+                }
+                space[i][j].energy = 0;
+                space[i][j].lock = true;
+            }
+        }
+    } while (n_flashes > 0);
+
+    ITER_SPACE(i, j)
+    {
+        if (space[i][j].lock)
+        {
+            n_flashes++;
+            space[i][j].lock = false;
+        }
+    }
+    return n_flashes;
+}
+
+void increment_energy(SPACE space)
+{
+    ITER_SPACE(i, j)
+    {
+        space[i][j].energy++;
+    }
+}
+
+void print_space(SPACE space)
+{
+    for (size_t i = 0; i < SPACE_SIZE; i++)
+    {
+        for (size_t j = 0; j < SPACE_SIZE; j++)
+        {
+            if (space[i][j].energy)
+                printf("%d ", space[i][j].energy);
+            else
+                printf("* ");
+        }
+        putchar('\n');
+    }
+    putchar('\n');
+}
+
+SPACE new_space(void)
+{
+    SPACE space = calloc(SPACE_SIZE, sizeof(OCTOPUS *));
+    CHECK_ALLOC(space);
+    for (size_t i = 0; i < SPACE_SIZE; i++)
+    {
+        space[i] = calloc(SPACE_SIZE, sizeof(OCTOPUS));
+        CHECK_ALLOC(space[i]);
+    }
+    return space;
+}
+
+//
+
+SPACE read_file(char *file)
+{
+    SPACE space = new_space();
+    FILE *p_file = fopen(file, "r");
+    CHECK_ALLOC(p_file);
+    char buf[BUFSIZ];
+    size_t j = 0;
+    while (fgets(buf, sizeof buf, p_file) != NULL)
+    {
+        for (size_t i = 0; i < SPACE_SIZE; i++)
+        {
+            space[j][i].energy = buf[i] - '0';
+        }
+        j++;
+    }
+    return space;
+}
+
+int main(void)
+{
+    SPACE space = read_file("input");
+    size_t total_flashes = 0;
+#ifdef PART_2
+    size_t step = 0;
+    for (; !check_sync(space); step++)
+#else
+    for (size_t i = 0; i < 100; i++)
+#endif
+    {
+        increment_energy(space);
+        total_flashes += flash(space);
+        // print_space(space);
+    }
+#ifdef PART_2
+    printf("SYNC STEP %zu\n", step);
+#else
+    printf("FLASHES %zu\n", total_flashes);
+#endif
+}
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