diff --git a/include/field.h b/include/field.h
index a109b14..4e8dfd7 100755
--- a/include/field.h
+++ b/include/field.h
@@ -19,12 +19,10 @@ private:
     size_t FieldSize = 4;
     std::vector<Line> field;
 
-    std::vector<Tile> processLine(const std::vector<Tile> &sourceLine, Score &score);
-
-    Line getRow(size_t rowIndex) const;
-    std::vector<Tile> getColumn(size_t columnIndex) const;
-    void setRow(size_t rowIndex, const std::vector<Tile> &line);
-    void setColumn(size_t columnIndex, const std::vector<Tile> &line);
+    Line& getRow(size_t rowIndex) const;
+    Line& getColumn(size_t columnIndex) const;
+    void setRow(size_t rowIndex, const Line &line);
+    void setColumn(size_t columnIndex, const Line &line);
 
     void reset();
     void setSize(size_t size);
diff --git a/include/line.h b/include/line.h
index 98f18c8..f60ee74 100644
--- a/include/line.h
+++ b/include/line.h
@@ -10,4 +10,18 @@ struct Line {
     Line(size_t length);
 
     void process();
+
+    void push_back(Tile tile);
+    size_t size();
+    size_t size() const;
+
+    Tile& operator[](size_t index);
+    const Tile& operator[](size_t index) const;
+    bool operator==(const Line &other) const;
+    bool operator!=(const Line &other) const;
+
+    std::vector<Tile>::iterator begin();
+    std::vector<Tile>::iterator end();
+    std::vector<Tile>::const_iterator begin() const;
+    std::vector<Tile>::const_iterator end() const;
 };
\ No newline at end of file
diff --git a/main.cpp b/main.cpp
index e378372..818aaea 100755
--- a/main.cpp
+++ b/main.cpp
@@ -16,19 +16,19 @@ int main() {
         {
         case 'w':
             field.moveUp();
-            field.spawnTile();
+            field.spawnTile(field.getEmptyTiles());
             break;
         case 's':
             field.moveDown();
-            field.spawnTile();
+            field.spawnTile(field.getEmptyTiles());
             break;
         case 'a':
             field.moveLeft();
-            field.spawnTile();
+            field.spawnTile(field.getEmptyTiles());
             break;
         case 'd':
             field.moveRight();
-            field.spawnTile();
+            field.spawnTile(field.getEmptyTiles());
             break;
         default:
             return 0;
diff --git a/source/field.cpp b/source/field.cpp
index ca84ef1..04e2d6c 100755
--- a/source/field.cpp
+++ b/source/field.cpp
@@ -20,60 +20,24 @@ Public methods:
 */
 
 // PRIVATE
-std::vector<Tile> Field::processLine(const std::vector<Tile>& sourceLine, Score &score) {
-    std::vector<Tile> result;
-    Tile pending = 0;
-    bool hasPending = false;
-    
-    for (Tile element : sourceLine) {
-        if (element == 0) continue;
-        
-        if (!hasPending) {
-            pending = element;
-            hasPending = true;
-            continue;
-        }
-        
-        if (element == pending) {
-            result.push_back(pending * 2);
-            score += pending * 2;
-            hasPending = false;
-            pending = 0;
-        } else {
-            result.push_back(pending);
-            pending = element;
-        }
-    }
-    
-    if (hasPending) {
-        result.push_back(pending);
-    }
-    
-    while (result.size() < sourceLine.size()) {
-        result.push_back(0);
-    }
-    
-    return result;
-}
-
-Line Field::getRow(size_t rowIndex) const {
+Line& Field::getRow(size_t rowIndex) const {
     return this->field[rowIndex];
 }
 
-std::vector<Tile> Field::getColumn(size_t columnIndex) const {
+Line& Field::getColumn(size_t columnIndex) const {
     // from top to bottom
-    std::vector<Tile> column;
+    Line column;
     for (size_t i = 0; i < this->FieldSize; ++i) {
         column.push_back(this->field[i][columnIndex]);
     }
     return column;
 }
 
-void Field::setRow(size_t rowIndex, const std::vector<Tile> &line) {
+void Field::setRow(size_t rowIndex, const Line &line) {
     this->field[rowIndex] = line;
 }
 
-void Field::setColumn(size_t columnIndex, const std::vector<Tile> &line) {
+void Field::setColumn(size_t columnIndex, const Line &line) {
     // from top to bottom (same)
     for (size_t i = 0; i < this->FieldSize; ++i) {
         this->field[i][columnIndex] = line[i];
@@ -81,7 +45,10 @@ void Field::setColumn(size_t columnIndex, const std::vector<Tile> &line) {
 }
 
 void Field::reset() {
-    this->field.resize(this->FieldSize, std::vector<Tile>(this->FieldSize, 0));
+    this->field.resize(this->FieldSize);
+    for (size_t i = 0; i < this->FieldSize; ++i) {
+        this->field[i] = Line(this->FieldSize);
+    }
 }
 
 // PUBLIC
@@ -89,7 +56,7 @@ Field::Field(size_t fieldSize) : mt(std::random_device{}()), FieldSize(fieldSize
     this->reset();
 }
 
-void printVector(const std::vector<Tile> &arr) {
+void printVector(const Line &arr) {
     for (size_t i = 0; i < arr.size(); ++i) {
         printf("%llu ", arr[i]);
     }
@@ -99,9 +66,9 @@ void printVector(const std::vector<Tile> &arr) {
 bool Field::moveUp() {
     auto oldField = this->field;
     for (size_t i = 0; i < this->FieldSize; ++i) {
-        std::vector<Tile> column;
+        Line column;
         column = getColumn(i);
-        column = processLine(column, this->score);
+        column.process();
         setColumn(i, column);
     }
     return this->field != oldField;
@@ -110,10 +77,10 @@ bool Field::moveUp() {
 bool Field::moveDown() {
     auto oldField = this->field;
     for (size_t i = 0; i < this->FieldSize; ++i) {
-        std::vector<Tile> column;
+        Line column;
         column = getColumn(i);
         std::reverse(column.begin(), column.end());
-        column = processLine(column, this->score);
+        column.process();
         std::reverse(column.begin(), column.end());
         setColumn(i, column);
     }
@@ -122,10 +89,10 @@ bool Field::moveDown() {
 
 bool Field::moveLeft() {
     auto oldField = this->field;
-    std::vector<Tile> row;
+    Line row;
     for (size_t i = 0; i < this->FieldSize; ++i) {
         row = getRow(i);
-        row = processLine(row, this->score);
+        row.process();
         setRow(i, row);
     }
     return this->field != oldField;
@@ -133,11 +100,11 @@ bool Field::moveLeft() {
 
 bool Field::moveRight() {
     auto oldField = this->field;
-    std::vector<Tile> row;
+    Line row;
     for (size_t i = 0; i < this->FieldSize; ++i) {
         row = getRow(i);
         std::reverse(row.begin(), row.end());
-        row = processLine(row, this->score);
+        row.process();
         std::reverse(row.begin(), row.end());
         setRow(i, row);
     }
diff --git a/source/line.cpp b/source/line.cpp
index e713e9c..92755f6 100644
--- a/source/line.cpp
+++ b/source/line.cpp
@@ -1,5 +1,11 @@
 #include "line.h"
 
+/*
+Fields:
+    std::vector<Tile> line;
+    Score score;
+*/
+
 Line::Line() {
     this->line.clear();
     this->line.reserve(4);
@@ -10,7 +16,7 @@ Line::Line(size_t length) {
     this->line.reserve(length);
 }
 
-void Line::processLine() {
+void Line::process() {
     std::vector<Tile> result;
     Tile pending = 0;
     bool hasPending = false;
@@ -39,9 +45,56 @@ void Line::processLine() {
         result.push_back(pending);
     }
     
-    while (result.size() < sourceLine.size()) {
+    while (result.size() < this->line.size()) {
         result.push_back(0);
     }
     
-    return result;
+    this->line = result;
+}
+
+// base methods
+void Line::push_back(Tile tile) {
+    this->line.push_back(tile);
+}
+
+size_t Line::size() {
+    return this->line.size();
+}
+
+size_t Line::size() const {
+    return this->line.size();
+}
+
+// overloadings
+Tile& Line::operator[](size_t index) {
+    return this->line[index];
+}
+
+const Tile& Line::operator[](size_t index) const {
+    return this->line[index];
+}
+
+bool Line::operator==(const Line &other) const {
+    return this->line == other.line && this->score == other.score;
+}
+
+bool Line::operator!=(const Line &other) const {
+    return !(*this == other);
+}
+
+// iterators
+std::vector<Tile>::iterator Line::begin() {
+    return this->line.begin();
+}
+
+std::vector<Tile>::iterator Line::end() {
+    return this->line.end();
+}
+
+std::vector<Tile>::const_iterator Line::begin() const {
+    return this->line.begin();
+}
+
+std::vector<Tile>::const_iterator Line::end() const {
+    return this->line.end();
 }
\ No newline at end of file