diff --git a/battleships.c b/battleships.c
index 7f8b38e..29bdedf 100644
--- a/battleships.c
+++ b/battleships.c
@@ -1,10 +1,15 @@
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
+#include <ctype.h>
 
 enum {
-    N_SHIPS,
-    WIDTH = 8,
-    HEIGHT = 8,
+  BOARD_SIZE = 10,
+};
+
+struct state {
+    char board[BOARD_SIZE][BOARD_SIZE];
+    int game_over;
 };
 
 struct position {
@@ -12,69 +17,163 @@ struct position {
     int y;
 };
 
-struct ship {
-    int length;
+enum orientation {
+  O_VERTICAL,
+  O_HORIZONTAL
+};
+
+struct boat {
+    enum orientation orientation;
+
+    /** left upper corner */
     struct position position;
-    char sunken;
-    char alignment;
-    char *hits;
+
+    int length;
 };
 
-struct game_state {
-    char running;
-    char board[WIDTH][HEIGHT];
-    struct ship ships[N_SHIPS];
+struct position read_position(void);
+
+struct boat generate_boat(int length);
+
+struct state generate_state(void);
+
+void display_state(struct state state);
+
+int valid_position(struct position p);
+
+/**
+ * Simulates one step of battleship.
+ *
+ * Performs the following steps:
+ *
+ * - apply hit to board
+ * - check sunken ships
+ * - check game over
+ */
+void update_state(struct state * state, struct position hit);
+
+enum target {
+   T_WATER,
+   T_BOAT,
 };
 
-struct ship create_ship(int length, struct position position);
-void delete_ship(struct ship ship);
-
-void hit(struct game_state *game_state, struct position position);
-
-struct game_state init_game_state();
-void deinit_game_state(struct game_state *game_state);
-char check_win_condition(struct game_state *game_state);
-
-struct position read_position();
+enum target check_hit(struct state state, struct position hit);
 
 int main(void) {
-    struct game_state game_state = init_game_state();
-    while (game_state.running) {
-        struct position hit_position = read_position();
-        hit(&game_state, hit_position);
-        if (check_win_condition(&game_state)) {
-            game_state.running = 0;
-            printf("You win!");
+    struct state state = generate_state();
+
+    while (!state.game_over) {
+        display_state(state);
+
+        struct position hit = read_position();
+
+        /* game logic */
+        update_state(&state, hit);
+    }
+}
+
+struct position read_position(void) {
+    printf("enter coordinate: ");
+    while (1) {
+        char* line = NULL;
+        size_t size = 0;
+        getline(&line, &size, stdin);
+        fflush(stdout);
+
+        struct position position;
+        char col;
+        sscanf("%c%d", &col, &position.y);
+        free(line);
+
+        position.x = tolower(col) - 'a';
+        if (valid_position(position)) {
+            return position;
         }
-    }
-    deinit_game_state(&game_state);
-    return 0;
-}
 
-struct ship create_ship(int length, struct position position) {
-    struct ship ship = {.length = length, .position = position, .sunken = 0};
-    ship.hits = calloc(length, sizeof *ship.hits);
-    return ship;
-}
-void delete_ship(struct ship ship) {
-    free(ship.hits);
-}
-
-void hit(struct game_state *game_state, struct position position);
-
-struct game_state init_game_state() {
-    struct game_state game_state;
-    for (int i = 0; i < N_SHIPS; ++i) {
-        /* generate ship */
+        puts("invalid input!");
     }
 }
 
-void deinit_game_state(struct game_state *game_state) {
-    for (int i = 0; i < N_SHIPS; ++i) {
-        delete_ship(game_state->ships[i]);
-    }
+struct position random_position(void) {
+    struct position p;
+    p.x = rand() % BOARD_SIZE;
+    p.y = rand() % BOARD_SIZE;
+    return p;
 }
 
-char check_win_condition(struct game_state *game_state);
+enum orientation random_orientation(void) {
+    return (rand() % 2);
+}
 
-struct position read_position();
+struct boat generate_boat(int length) {
+    struct boat b;
+    b.length = length;
+    b.position = random_position();
+    b.orientation = random_orientation();
+    return b;
+}
+
+int valid_position(struct position p) {
+    return (p.x >= 0) && (p.x < BOARD_SIZE) && (p.y >= 0) && (p.y < BOARD_SIZE);
+}
+
+int place_boat(struct state * state, struct boat boat, char c) {
+    int dx = (boat.orientation == O_VERTICAL) ? 1 : 0;
+    int dy = (boat.orientation == O_HORIZONTAL) ? 1 : 0;
+
+    struct position curpos = boat.position;
+    for (int i = 0; i < boat.length; ++i) {
+        if (!valid_position(curpos)) return 0;
+        if (state->board[curpos.y][curpos.x] != 0) return 0;
+
+        if (c) {
+            state->board[curpos.y][curpos.x] = c;
+        }
+
+        curpos.x += dx;
+        curpos.y += dy;
+    }
+
+    return 1;
+}
+
+const int BOAT_LENGTHS[] = { 5, 4, 4, 3, 3, 3, 2, 2, 2, 2 };
+
+struct state generate_state(void) {
+  struct state state;
+
+  memset(state.board, 0, BOARD_SIZE*BOARD_SIZE);
+  state.game_over = 0;
+
+  // generate some boats
+  char boat_char = 'A';
+  for (size_t i = 0; i < sizeof(BOAT_LENGTHS) / sizeof(BOAT_LENGTHS[0]); ++i) {
+      int length = BOAT_LENGTHS[i];
+      struct boat boat;
+      do {
+          boat = generate_boat(length);
+      } while(!place_boat(&state, boat, '\0'));
+      place_boat(&state, boat, boat_char);
+      boat_char++;
+  }
+
+  return state;
+}
+
+void display_state(struct state state) {
+    for (int y = 0; y < BOARD_SIZE; ++y) {
+        for (int x = 0; x < BOARD_SIZE; ++x) {
+            if (state.board[y][x]) {
+                printf("%c", state.board[y][x]);
+            } else {
+                printf("~");
+            }
+        }
+        printf("\n");
+    }
+    puts("---");
+}
+
+void update_state(struct state * state, struct position hit) {
+
+}
diff --git a/battleships_manuel.c b/battleships_manuel.c
new file mode 100644
index 0000000..7f8b38e
--- /dev/null
+++ b/battleships_manuel.c
@@ -0,0 +1,80 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+enum {
+    N_SHIPS,
+    WIDTH = 8,
+    HEIGHT = 8,
+};
+
+struct position {
+    int x;
+    int y;
+};
+
+struct ship {
+    int length;
+    struct position position;
+    char sunken;
+    char alignment;
+    char *hits;
+};
+
+struct game_state {
+    char running;
+    char board[WIDTH][HEIGHT];
+    struct ship ships[N_SHIPS];
+};
+
+struct ship create_ship(int length, struct position position);
+void delete_ship(struct ship ship);
+
+void hit(struct game_state *game_state, struct position position);
+
+struct game_state init_game_state();
+void deinit_game_state(struct game_state *game_state);
+char check_win_condition(struct game_state *game_state);
+
+struct position read_position();
+
+int main(void) {
+    struct game_state game_state = init_game_state();
+    while (game_state.running) {
+        struct position hit_position = read_position();
+        hit(&game_state, hit_position);
+        if (check_win_condition(&game_state)) {
+            game_state.running = 0;
+            printf("You win!");
+        }
+    }
+    deinit_game_state(&game_state);
+    return 0;
+}
+
+struct ship create_ship(int length, struct position position) {
+    struct ship ship = {.length = length, .position = position, .sunken = 0};
+    ship.hits = calloc(length, sizeof *ship.hits);
+    return ship;
+}
+void delete_ship(struct ship ship) {
+    free(ship.hits);
+}
+
+void hit(struct game_state *game_state, struct position position);
+
+struct game_state init_game_state() {
+    struct game_state game_state;
+    for (int i = 0; i < N_SHIPS; ++i) {
+        /* generate ship */
+    }
+}
+
+void deinit_game_state(struct game_state *game_state) {
+    for (int i = 0; i < N_SHIPS; ++i) {
+        delete_ship(game_state->ships[i]);
+    }
+}
+
+char check_win_condition(struct game_state *game_state);
+
+struct position read_position();