diff --git a/app/main.py b/app/main.py
index 626f41cf..45861ee9 100644
--- a/app/main.py
+++ b/app/main.py
@@ -1,34 +1,101 @@
+from typing import List, Tuple, Optional, Dict
+
+
 class Deck:
-    def __init__(self, row, column, is_alive=True):
-        pass
+    def __init__(self, row: int, column: int, is_alive: bool = True) -> None:
+        self.row = row
+        self.column = column
+        self.is_alive = is_alive
 
 
 class Ship:
-    def __init__(self, start, end, is_drowned=False):
-        # Create decks and save them to a list `self.decks`
-        pass
+    def __init__(
+        self,
+        start: Tuple[int, int],
+        end: Tuple[int, int],
+        is_drowned: bool = False
+    ) -> None:
+        if start[0] != end[0] and start[1] != end[1]:
+            raise ValueError("Ships must be straight lines")
+
+        self.is_drowned = is_drowned
+        self.decks: List[Deck] = []
+
+        row_start, row_end = min(start[0], end[0]), max(start[0], end[0])
+        col_start, col_end = min(start[1], end[1]), max(start[1], end[1])
+
+        for row_idx in range(row_start, row_end + 1):
+            for col_idx in range(col_start, col_end + 1):
+                self.decks.append(Deck(row_idx, col_idx))
 
-    def get_deck(self, row, column):
-        # Find the corresponding deck in the list
-        pass
+    def get_deck(self, row: int, column: int) -> Optional[Deck]:
+        for deck in self.decks:
+            if deck.row == row and deck.column == column:
+                return deck
+        return None
 
-    def fire(self, row, column):
-        # Change the `is_alive` status of the deck
-        # And update the `is_drowned` value if it's needed
-        pass
+    def fire(self, row: int, column: int) -> None:
+        target_deck = self.get_deck(row, column)
+        if target_deck is not None:
+            target_deck.is_alive = False
+            self.is_drowned = all(not d.is_alive for d in self.decks)
 
 
 class Battleship:
-    def __init__(self, ships):
-        # Create a dict `self.field`.
-        # Its keys are tuples - the coordinates of the non-empty cells,
-        # A value for each cell is a reference to the ship
-        # which is located in it
-        pass
-
-    def fire(self, location: tuple):
-        # This function should check whether the location
-        # is a key in the `self.field`
-        # If it is, then it should check if this cell is the last alive
-        # in the ship or not.
-        pass
+    def __init__(
+        self,
+        ships: List[Tuple[Tuple[int, int], Tuple[int, int]]]
+    ) -> None:
+        self.field: Dict[Tuple[int, int], Ship] = {}
+        self.ships_list: List[Ship] = []
+
+        for start, end in ships:
+            new_ship = Ship(start, end)
+
+            for deck in new_ship.decks:
+                if not (0 <= deck.row <= 9 and 0 <= deck.column <= 9):
+                    raise ValueError("Coordinates out of range (0-9)")
+
+                if (deck.row, deck.column) in self.field:
+                    raise ValueError("Ships must not overlap")
+
+                self.field[(deck.row, deck.column)] = new_ship
+
+            self.ships_list.append(new_ship)
+
+        self._validate_field()
+
+    def fire(self, location: Tuple[int, int]) -> str:
+        if location not in self.field:
+            return "Miss!"
+
+        ship = self.field[location]
+        ship.fire(location[0], location[1])
+
+        if ship.is_drowned:
+            return "Sunk!"
+
+        return "Hit!"
+
+    def _validate_field(self) -> None:
+        if len(self.ships_list) != 10:
+            raise ValueError("Fleet must have exactly 10 ships")
+
+        ship_sizes = sorted(
+            [len(ship.decks) for ship in self.ships_list], reverse=True
+        )
+        if ship_sizes != [4, 3, 3, 2, 2, 2, 1, 1, 1, 1]:
+            raise ValueError("Invalid ship sizes composition")
+
+        for ship in self.ships_list:
+            for deck in ship.decks:
+                for dr in range(-1, 2):
+                    for dc in range(-1, 2):
+                        if dr == 0 and dc == 0:
+                            continue
+
+                        neighbor_pos = (deck.row + dr, deck.column + dc)
+
+                        if neighbor_pos in self.field:
+                            if self.field[neighbor_pos] != ship:
+                                raise ValueError("Ships are touching!")