diff --git a/src/app/App.tsx b/src/app/App.tsx
index 8e7f36c..c8f597b 100644
--- a/src/app/App.tsx
+++ b/src/app/App.tsx
@@ -10,12 +10,16 @@ const App: React.FC = () => {
   return (
     <ThemeProvider>
       <TodoProvider>
-        <div className="app-container">
+        <div className="app-wrapper">
           <header className="app-header">
-            <FileSelector />
-            <ThemeToggle />
+            <div className="app-header-content">
+              <FileSelector />
+              <ThemeToggle />
+            </div>
           </header>
-          <TodoList />
+          <div className="app-container">
+            <TodoList />
+          </div>
         </div>
       </TodoProvider>
     </ThemeProvider>
diff --git a/src/app/components/AddTodoForm/style.css b/src/app/components/AddTodoForm/style.css
index 8673f17..4109320 100644
--- a/src/app/components/AddTodoForm/style.css
+++ b/src/app/components/AddTodoForm/style.css
@@ -1,24 +1,63 @@
 .add-todo-form {
   display: flex;
-  justify-content: space-between;
-  border-left: 4px solid var(--primary-color);
-  padding: 5px;
+  gap: 0.75rem;
+  padding: 1.5rem;
+  background-color: var(--card-background);
+  border-radius: var(--radius-lg);
+  box-shadow: var(--shadow-sm);
+  margin-top: 1.5rem;
+}
+
+@media (max-width: 768px) {
+  .add-todo-form {
+    padding: 1rem;
+    gap: 0.5rem;
+  }
 }
 
 .add-todo-form input {
   flex: 1;
-  padding: 10px;
-  border: none;
-  border-bottom: 1px solid var(--primary-color);
-  background-color: transparent;
+  padding: 0.75rem 1rem;
+  border: 2px solid var(--border-color);
+  border-radius: var(--radius-md);
+  background-color: var(--secondary-color);
   color: var(--text-color);
+  font-size: 1rem;
+  transition: all 0.2s ease;
+}
+
+.add-todo-form input:focus {
+  outline: none;
+  border-color: var(--primary-color);
+  box-shadow: 0 0 0 3px rgb(59 130 246 / 0.1);
+}
+
+.add-todo-form input:hover {
+  border-color: var(--primary-color);
+}
+
+.add-todo-form input::placeholder {
+  color: var(--text-secondary);
 }
 
 .add-todo-form button {
-  margin-left: 5px;
-  padding: 10px 15px;
+  padding: 0.75rem 1.5rem;
   background-color: var(--primary-color);
-  color: var(--secondary-color);
+  color: white;
   border: none;
-  border-radius: 4px;
+  border-radius: var(--radius-md);
+  font-weight: var(--font-weight-medium);
+  cursor: pointer;
+  transition: all 0.2s ease;
+  box-shadow: var(--shadow-sm);
+}
+
+.add-todo-form button:hover {
+  background-color: var(--primary-hover);
+  transform: translateY(-1px);
+  box-shadow: var(--shadow-md);
+}
+
+.add-todo-form button:active {
+  transform: translateY(0);
 }
diff --git a/src/app/components/FileSelector/style.css b/src/app/components/FileSelector/style.css
index 2d295c3..98f59c2 100644
--- a/src/app/components/FileSelector/style.css
+++ b/src/app/components/FileSelector/style.css
@@ -1,78 +1,158 @@
+.file-selector {
+  display: flex;
+  align-items: center;
+  gap: 1rem;
+}
+
+@media (max-width: 768px) {
+  .file-selector {
+    flex-direction: column;
+    align-items: flex-start;
+    gap: 0.75rem;
+  }
+}
+
 .no-file-message {
   text-align: start;
 }
 
+.no-file-message p {
+  color: var(--text-color);
+  font-size: 1rem;
+  margin-bottom: 1rem;
+}
+
 .file-buttons {
   display: flex;
-  justify-content: start;
-  gap: 8px;
-  margin-top: 12px;
+  gap: 0.75rem;
+}
+
+@media (max-width: 768px) {
+  .file-buttons {
+    flex-wrap: wrap;
+    gap: 0.5rem;
+  }
 }
 
 .create-file-button,
 .change-file-button,
 .open-file-button {
-  padding: 8px 16px;
-  border-radius: 4px;
+  padding: 0.75rem 1.5rem;
+  border-radius: var(--radius-md);
   cursor: pointer;
-  font-weight: bold;
+  font-weight: var(--font-weight-medium);
   border: none;
+  transition: all 0.2s ease;
+  box-shadow: var(--shadow-sm);
+  font-size: 0.875rem;
 }
 
 .create-file-button {
   background-color: var(--primary-color);
-  color: var(--secondary-color);
+  color: white;
+}
+
+.create-file-button:hover {
+  background-color: var(--primary-hover);
+  transform: translateY(-1px);
+  box-shadow: var(--shadow-md);
 }
 
 .open-file-button {
   background-color: var(--secondary-color);
+  color: var(--text-color);
+  border: 2px solid var(--border-color);
+}
+
+.open-file-button:hover {
+  background-color: var(--background-color);
+  border-color: var(--primary-color);
   color: var(--primary-color);
+  transform: translateY(-1px);
+  box-shadow: var(--shadow-md);
 }
 
 .change-file-button {
   background-color: var(--secondary-color);
+  color: var(--text-color);
+  border: 2px solid var(--border-color);
+}
+
+.change-file-button:hover {
+  background-color: var(--background-color);
+  border-color: var(--primary-color);
   color: var(--primary-color);
+  transform: translateY(-1px);
+  box-shadow: var(--shadow-md);
 }
 
-.create-file-button:hover,
-.change-file-button:hover,
-.open-file-button:hover {
-  opacity: 0.9;
+.create-file-button:disabled,
+.change-file-button:disabled,
+.open-file-button:disabled {
+  opacity: 0.6;
+  cursor: not-allowed;
+  transform: none;
 }
 
 .file-selected {
   display: flex;
   align-items: center;
-  justify-content: space-between;
+  gap: 1rem;
+}
+
+.file-info {
+  display: flex;
+  flex-direction: column;
+  gap: 0.75rem;
 }
 
 .file-name {
   color: var(--text-color);
   font-size: 0.95rem;
+  display: flex;
+  align-items: center;
+  gap: 0.5rem;
+}
+
+.file-name strong {
+  font-weight: var(--font-weight-medium);
 }
 
 .save-status {
-  font-size: 0.9rem;
+  color: var(--success-color);
+  font-size: 0.875rem;
+  font-weight: var(--font-weight-medium);
 }
 
 .browser-warning {
-  background-color: #fff3cd;
-  color: #856404;
-  padding: 5px;
-  border-radius: 4px;
-  margin-bottom: 10px;
+  background-color: #fef3c7;
+  color: #92400e;
+  padding: 1rem;
+  border-radius: var(--radius-md);
+  margin-bottom: 1rem;
+  border: 1px solid #f59e0b;
+}
+
+.browser-warning p {
+  margin: 0;
+  font-size: 0.875rem;
 }
 
 .error-message {
-  background-color: #f8d7da;
-  color: #721c24;
-  padding: 5px;
-  border-radius: 4px;
-  margin-bottom: 10px;
+  background-color: #fef2f2;
+  color: #991b1b;
+  padding: 1rem;
+  border-radius: var(--radius-md);
+  margin-bottom: 1rem;
+  border: 1px solid var(--error-color);
 }
 
-.file-selected {
-  display: flex;
-  align-items: center;
-  justify-content: space-between;
+.error-message p {
+  margin: 0;
+  font-size: 0.875rem;
+}
+
+.loading-message {
+  color: var(--text-secondary);
+  font-size: 0.875rem;
 }
diff --git a/src/app/components/ThemeToggle/style.css b/src/app/components/ThemeToggle/style.css
index bd1b13f..5cdb354 100644
--- a/src/app/components/ThemeToggle/style.css
+++ b/src/app/components/ThemeToggle/style.css
@@ -1,8 +1,24 @@
 .theme-toggle {
-    padding: 0.5rem;
-    font-size: 1.5rem;
-    border: none;
-    background-color: transparent;
-    cursor: pointer;
-    z-index: 100;
-}
\ No newline at end of file
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  width: 3rem;
+  height: 3rem;
+  border: 1px solid var(--border-color);
+  background-color: var(--card-background);
+  border-radius: var(--radius-md);
+  cursor: pointer;
+  transition: all 0.2s ease;
+  box-shadow: var(--shadow-sm);
+  font-size: 1.25rem;
+}
+
+.theme-toggle:hover {
+  background-color: var(--border-color);
+  transform: translateY(-1px);
+  box-shadow: var(--shadow-md);
+}
+
+.theme-toggle:active {
+  transform: translateY(0);
+}
diff --git a/src/app/components/TodoItem/style.css b/src/app/components/TodoItem/style.css
index fbe62d1..05b407e 100644
--- a/src/app/components/TodoItem/style.css
+++ b/src/app/components/TodoItem/style.css
@@ -1,195 +1,288 @@
-.time-spent.editable {
-  cursor: pointer;
-  text-decoration: underline dotted;
+.todo-item {
+  display: flex;
+  flex-direction: column;
+  gap: 0.75rem;
+  padding: 1.25rem;
+  background-color: var(--card-background);
+  border-radius: var(--radius-md);
+  box-shadow: var(--shadow-sm);
+  transition: all 0.2s ease;
 }
 
-.time-spent.editable:hover {
-  color: var(--primary-color);
+.todo-item:hover {
+  box-shadow: var(--shadow-md);
+  transform: translateY(-1px);
 }
 
-.time-edit {
+@media (max-width: 768px) {
+  .todo-item {
+    padding: 1rem;
+  }
+}
+
+.todo-header,
+.todo-content {
   display: flex;
   align-items: center;
+  gap: 0.75rem;
 }
 
-.time-input {
-  width: 40px;
-  padding: 2px 4px;
-  text-align: center;
-  border: none;
-  border-bottom: 1px solid var(--primary-color);
+.todo-number {
+  font-family: 'JetBrains Mono', monospace;
+  font-weight: var(--font-weight-medium);
+  color: var(--text-secondary);
+  font-size: 0.875rem;
+  background-color: var(--border-color);
+  padding: 0.25rem 0.5rem;
+  border-radius: var(--radius-sm);
+  flex-shrink: 0;
 }
 
-.time-save-btn,
-.time-cancel-btn {
-  width: 24px;
-  height: 24px;
-  margin-left: 2px;
-  border-radius: 50%;
-  border: 1px solid var(--border-color);
-  background-color: var(--card-background);
-  cursor: pointer;
-  font-size: 0.8rem;
+.todo-status {
+  flex-shrink: 0;
 }
 
-.time-cancel-btn:hover,
-.time-save-btn:hover {
-  background-color: var(--primary-color);
-  color: var(--secondary-color);
+.todo-status select {
+  padding: 0.5rem 0.75rem;
+  border: 2px solid var(--border-color);
+  border-radius: var(--radius-sm);
+  background-color: var(--secondary-color);
+  color: var(--text-color);
+  font-size: 0.875rem;
+  cursor: pointer;
+  transition: all 0.2s ease;
+  font-weight: var(--font-weight-medium);
 }
 
-.time-spent.counting {
-  color: #4caf50;
-  font-weight: bold;
-  animation: pulse 1s infinite alternate;
+.todo-status select:focus {
+  outline: none;
+  border-color: var(--primary-color);
+  box-shadow: 0 0 0 3px rgb(59 130 246 / 0.1);
 }
 
-.time-tracking {
-  margin-left: auto;
-  display: flex;
-  align-items: center;
-  gap: 8px;
+.todo-status select:hover {
+  border-color: var(--primary-color);
+  background-color: var(--background-color);
 }
 
-.time-spent {
-  font-family: monospace;
+.todo-text {
+  flex-grow: 1;
+  font-size: 1rem;
+  color: var(--text-color);
+  line-height: 1.5;
 }
 
-.start-button, .pause-button {
-  padding: 3px 8px;
-  border-radius: 4px;
+.todo-text.editable {
   cursor: pointer;
-  font-size: 0.8rem;
+  padding: 0.25rem 0.5rem;
+  border-radius: var(--radius-sm);
+  transition: all 0.2s ease;
 }
 
-.start-button {
-  background-color: var(--primary-color);
-  color: var(--secondary-color);
-  border: none;
+.todo-text.editable:hover {
+  background-color: var(--border-color);
+  color: var(--primary-color);
 }
 
-.pause-button {
-  background-color: var(--primary-color);
-  color: var(--secondary-color);
-  border: none;
+.todo-text-edit {
+  display: flex;
+  align-items: center;
+  flex-grow: 1;
+  gap: 0.5rem;
 }
 
-.todo-item {
-  display: flex;
-  flex-direction: column;
-  gap: 6px;
-  padding: 5px 5px;
-  border-left: 4px solid;
+.text-input {
+  flex-grow: 1;
+  padding: 0.5rem 0.75rem;
+  border: 2px solid var(--border-color);
+  border-radius: var(--radius-sm);
+  background-color: var(--secondary-color);
+  color: var(--text-color);
+  font-size: 1rem;
 }
 
-.todo-header,
-.todo-content {
+.text-input:focus {
+  outline: none;
+  border-color: var(--primary-color);
+  box-shadow: 0 0 0 3px rgb(59 130 246 / 0.1);
+}
+
+.text-save-btn, 
+.text-cancel-btn {
+  width: 2rem;
+  height: 2rem;
   display: flex;
   align-items: center;
-  gap: 8px;
+  justify-content: center;
+  border-radius: var(--radius-sm);
+  border: 1px solid var(--border-color);
+  background-color: var(--card-background);
+  cursor: pointer;
+  font-size: 0.875rem;
+  transition: all 0.2s ease;
 }
 
-.todo-number {
-  font-family: monospace;
-  font-weight: bold;
-  color: var(--text-color);
-  flex-shrink: 0;
+.text-save-btn:hover {
+  background-color: var(--success-color);
+  color: white;
+  border-color: var(--success-color);
 }
 
-.todo-status {
-  flex-shrink: 0;
+.text-cancel-btn:hover {
+  background-color: var(--error-color);
+  color: white;
+  border-color: var(--error-color);
 }
 
-.todo-status select {
-  width: 100%;
-  padding: 4px;
-  border: none;
-  border-bottom: 1px solid var(--primary-color);
-  background-color: transparent;
-  color: var(--text-color);
+.time-tracking {
+  margin-left: auto;
+  display: flex;
+  align-items: center;
+  gap: 0.75rem;
 }
 
-.todo-text {
-  flex-grow: 1;
-  overflow: hidden;
-  text-overflow: ellipsis;
-  white-space: nowrap;
+.time-spent {
+  font-family: 'JetBrains Mono', monospace;
+  font-size: 0.875rem;
+  color: var(--text-secondary);
+  font-weight: var(--font-weight-medium);
 }
 
-.todo-text.editable {
+.time-spent.editable {
   cursor: pointer;
+  padding: 0.25rem 0.5rem;
+  border-radius: var(--radius-sm);
+  transition: all 0.2s ease;
 }
 
-.todo-text.editable:hover {
-  text-decoration: underline dashed;
+.time-spent.editable:hover {
+  background-color: var(--border-color);
   color: var(--primary-color);
 }
 
-.todo-text-edit {
+.time-spent.counting {
+  color: var(--success-color);
+  font-weight: var(--font-weight-bold);
+  animation: pulse 1s infinite alternate;
+}
+
+.time-edit {
   display: flex;
   align-items: center;
-  flex-grow: 1;
+  gap: 0.5rem;
 }
 
-.text-input {
-  flex-grow: 1;
-  padding: 4px 8px;
-  border: none;
-  border-bottom: 1px solid var(--primary-color);
+.time-input {
+  width: 3rem;
+  padding: 0.25rem 0.5rem;
+  text-align: center;
+  border: 2px solid var(--border-color);
+  border-radius: var(--radius-sm);
+  background-color: var(--secondary-color);
+  color: var(--text-color);
+  font-size: 0.875rem;
+}
+
+.time-input:focus {
+  outline: none;
+  border-color: var(--primary-color);
+  box-shadow: 0 0 0 3px rgb(59 130 246 / 0.1);
 }
 
-.text-save-btn, .text-cancel-btn {
-  width: 24px;
-  height: 24px;
+.time-save-btn,
+.time-cancel-btn {
+  width: 2rem;
+  height: 2rem;
   display: flex;
   align-items: center;
   justify-content: center;
-  border-radius: 50%;
+  border-radius: var(--radius-sm);
   border: 1px solid var(--border-color);
   background-color: var(--card-background);
   cursor: pointer;
-  margin-left: 2px;
+  font-size: 0.875rem;
+  transition: all 0.2s ease;
 }
 
-.text-save-btn:hover {
-  background-color: var(--primary-color);
-  color: var(--secondary-color);
+.time-save-btn:hover {
+  background-color: var(--success-color);
+  color: white;
+  border-color: var(--success-color);
 }
 
-.text-cancel-btn:hover {
-  background-color: var(--primary-color);
-  color: var(--secondary-color);
+.time-cancel-btn:hover {
+  background-color: var(--error-color);
+  color: white;
+  border-color: var(--error-color);
+}
+
+.start-button, 
+.pause-button {
+  padding: 0.5rem 1rem;
+  border-radius: var(--radius-sm);
+  cursor: pointer;
+  font-size: 0.875rem;
+  font-weight: var(--font-weight-medium);
+  border: none;
+  transition: all 0.2s ease;
+  box-shadow: var(--shadow-sm);
+}
+
+.start-button {
+  background-color: var(--success-color);
+  color: white;
+}
+
+.start-button:hover {
+  background-color: #059669;
+  transform: translateY(-1px);
+  box-shadow: var(--shadow-md);
+}
+
+.pause-button {
+  background-color: var(--warning-color);
+  color: white;
+}
+
+.pause-button:hover {
+  background-color: #d97706;
+  transform: translateY(-1px);
+  box-shadow: var(--shadow-md);
 }
 
 .delete-button {
   background-color: transparent;
-  color: var(--text-color);
-  border: 1px solid var(--border-color);
-  border-radius: 4px;
-  padding: 4px 8px;
+  color: var(--error-color);
+  border: 1px solid var(--error-color);
+  border-radius: var(--radius-sm);
+  padding: 0.5rem 1rem;
   cursor: pointer;
-  transition: all 0.2s;
+  transition: all 0.2s ease;
   flex-shrink: 0;
+  font-size: 0.875rem;
+  font-weight: var(--font-weight-medium);
 }
 
 .delete-button:hover {
-  background-color: #ff4444;
+  background-color: var(--error-color);
   color: white;
+  transform: translateY(-1px);
+  box-shadow: var(--shadow-md);
 }
 
 .status-open {
-  border-left-color: #4a86e8;
+  border-left: 4px solid var(--primary-color);
 }
 
 .status-in-progress {
-  border-left-color: #fcba03;
+  border-left: 4px solid var(--warning-color);
 }
 
 .status-done {
-  border-left-color: #00c851;
+  border-left: 4px solid var(--success-color);
 }
 
 .completed .todo-text {
   text-decoration: line-through;
-  opacity: 0.7;
-}
\ No newline at end of file
+  color: var(--text-secondary);
+}
diff --git a/src/app/components/TodoItem/style.css.backup b/src/app/components/TodoItem/style.css.backup
new file mode 100644
index 0000000..fbe62d1
--- /dev/null
+++ b/src/app/components/TodoItem/style.css.backup
@@ -0,0 +1,195 @@
+.time-spent.editable {
+  cursor: pointer;
+  text-decoration: underline dotted;
+}
+
+.time-spent.editable:hover {
+  color: var(--primary-color);
+}
+
+.time-edit {
+  display: flex;
+  align-items: center;
+}
+
+.time-input {
+  width: 40px;
+  padding: 2px 4px;
+  text-align: center;
+  border: none;
+  border-bottom: 1px solid var(--primary-color);
+}
+
+.time-save-btn,
+.time-cancel-btn {
+  width: 24px;
+  height: 24px;
+  margin-left: 2px;
+  border-radius: 50%;
+  border: 1px solid var(--border-color);
+  background-color: var(--card-background);
+  cursor: pointer;
+  font-size: 0.8rem;
+}
+
+.time-cancel-btn:hover,
+.time-save-btn:hover {
+  background-color: var(--primary-color);
+  color: var(--secondary-color);
+}
+
+.time-spent.counting {
+  color: #4caf50;
+  font-weight: bold;
+  animation: pulse 1s infinite alternate;
+}
+
+.time-tracking {
+  margin-left: auto;
+  display: flex;
+  align-items: center;
+  gap: 8px;
+}
+
+.time-spent {
+  font-family: monospace;
+}
+
+.start-button, .pause-button {
+  padding: 3px 8px;
+  border-radius: 4px;
+  cursor: pointer;
+  font-size: 0.8rem;
+}
+
+.start-button {
+  background-color: var(--primary-color);
+  color: var(--secondary-color);
+  border: none;
+}
+
+.pause-button {
+  background-color: var(--primary-color);
+  color: var(--secondary-color);
+  border: none;
+}
+
+.todo-item {
+  display: flex;
+  flex-direction: column;
+  gap: 6px;
+  padding: 5px 5px;
+  border-left: 4px solid;
+}
+
+.todo-header,
+.todo-content {
+  display: flex;
+  align-items: center;
+  gap: 8px;
+}
+
+.todo-number {
+  font-family: monospace;
+  font-weight: bold;
+  color: var(--text-color);
+  flex-shrink: 0;
+}
+
+.todo-status {
+  flex-shrink: 0;
+}
+
+.todo-status select {
+  width: 100%;
+  padding: 4px;
+  border: none;
+  border-bottom: 1px solid var(--primary-color);
+  background-color: transparent;
+  color: var(--text-color);
+}
+
+.todo-text {
+  flex-grow: 1;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+
+.todo-text.editable {
+  cursor: pointer;
+}
+
+.todo-text.editable:hover {
+  text-decoration: underline dashed;
+  color: var(--primary-color);
+}
+
+.todo-text-edit {
+  display: flex;
+  align-items: center;
+  flex-grow: 1;
+}
+
+.text-input {
+  flex-grow: 1;
+  padding: 4px 8px;
+  border: none;
+  border-bottom: 1px solid var(--primary-color);
+}
+
+.text-save-btn, .text-cancel-btn {
+  width: 24px;
+  height: 24px;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  border-radius: 50%;
+  border: 1px solid var(--border-color);
+  background-color: var(--card-background);
+  cursor: pointer;
+  margin-left: 2px;
+}
+
+.text-save-btn:hover {
+  background-color: var(--primary-color);
+  color: var(--secondary-color);
+}
+
+.text-cancel-btn:hover {
+  background-color: var(--primary-color);
+  color: var(--secondary-color);
+}
+
+.delete-button {
+  background-color: transparent;
+  color: var(--text-color);
+  border: 1px solid var(--border-color);
+  border-radius: 4px;
+  padding: 4px 8px;
+  cursor: pointer;
+  transition: all 0.2s;
+  flex-shrink: 0;
+}
+
+.delete-button:hover {
+  background-color: #ff4444;
+  color: white;
+}
+
+.status-open {
+  border-left-color: #4a86e8;
+}
+
+.status-in-progress {
+  border-left-color: #fcba03;
+}
+
+.status-done {
+  border-left-color: #00c851;
+}
+
+.completed .todo-text {
+  text-decoration: line-through;
+  opacity: 0.7;
+}
\ No newline at end of file
diff --git a/src/app/components/TodoList/style.css b/src/app/components/TodoList/style.css
index 69e92f3..3a9f425 100644
--- a/src/app/components/TodoList/style.css
+++ b/src/app/components/TodoList/style.css
@@ -5,12 +5,46 @@
 .todo-lists-container {
   display: flex;
   flex-direction: column;
-  gap: 24px;
-  margin-top: 20px;
-  padding: 5px;
+  gap: 2rem;
+  padding: min(2rem, 4vw);
+  max-width: 1000px;
+  margin: 0 auto;
+}
+
+@media (max-width: 768px) {
+  .todo-lists-container {
+    padding: 1rem;
+    gap: 1.5rem;
+  }
 }
 
 .active-todos,
 .completed-todos {
   width: 100%;
+  background-color: var(--card-background);
+  border-radius: var(--radius-lg);
+  box-shadow: var(--shadow-md);
+  padding: 1.5rem;
+}
+
+@media (max-width: 768px) {
+  .active-todos,
+  .completed-todos {
+    padding: 1rem;
+  }
+}
+
+.active-todos h2,
+.completed-todos h2 {
+  color: var(--text-color);
+  font-size: 1.5rem;
+  font-weight: var(--font-weight-bold);
+  margin-bottom: 1.5rem;
+  padding-bottom: 0.75rem;
+}
+
+.todo-list {
+  display: flex;
+  flex-direction: column;
+  gap: 0.75rem;
 }
diff --git a/src/app/styles/theme.css b/src/app/styles/theme.css
index 4e1b2e3..22447a7 100644
--- a/src/app/styles/theme.css
+++ b/src/app/styles/theme.css
@@ -17,11 +17,24 @@
 }
 
 :root {
-  --background-color: #ffffff;
-  --text-color: #131313;
-  --border-color: #ffffff;
-  --primary-color: #000000;
+  --background-color: #fafafa;
+  --text-color: #1a1a1a;
+  --text-secondary: #6b7280;
+  --border-color: #e5e7eb;
+  --primary-color: #3b82f6;
+  --primary-hover: #2563eb;
   --secondary-color: #ffffff;
+  --card-background: #ffffff;
+  --card-border: #f3f4f6;
+  --success-color: #10b981;
+  --warning-color: #f59e0b;
+  --error-color: #ef4444;
+  --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
+  --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
+  --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
+  --radius-sm: 0.375rem;
+  --radius-md: 0.5rem;
+  --radius-lg: 0.75rem;
   --font-family: "Noto Sans Variable", -apple-system, BlinkMacSystemFont,
     "Segoe UI", Roboto, sans-serif;
   --font-weight-light: 300;
@@ -31,11 +44,21 @@
 }
 
 [data-theme="dark"] {
-  --background-color: #141414;
-  --text-color: #fcfcfc;
-  --border-color: #141414;
-  --primary-color: #ffffff;
-  --secondary-color: #141414;
+  --background-color: #0f172a;
+  --text-color: #f1f5f9;
+  --text-secondary: #94a3b8;
+  --border-color: #334155;
+  --primary-color: #3b82f6;
+  --primary-hover: #2563eb;
+  --secondary-color: #1e293b;
+  --card-background: #1e293b;
+  --card-border: #334155;
+  --success-color: #10b981;
+  --warning-color: #f59e0b;
+  --error-color: #ef4444;
+  --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.3);
+  --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.4), 0 2px 4px -2px rgb(0 0 0 / 0.4);
+  --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.4), 0 4px 6px -4px rgb(0 0 0 / 0.4);
 }
 
 body {
@@ -63,14 +86,43 @@ button {
   font-weight: var(--font-weight-medium);
 }
 
+.app-wrapper {
+  width: 100%;
+  min-height: 100vh;
+  background-color: var(--background-color);
+}
+
 .app-header {
+  width: 100%;
+  background-color: var(--card-background);
+  border-bottom: 1px solid var(--border-color);
+  box-shadow: var(--shadow-sm);
+}
+
+.app-header-content {
   display: flex;
   justify-content: space-between;
   align-items: center;
-  padding: 10px;
+  padding: 1.5rem min(2rem, 4vw);
+  max-width: 1200px;
+  margin: 0 auto;
+}
+
+@media (max-width: 768px) {
+  .app-header-content {
+    padding: 1rem;
+  }
 }
 
 .app-container {
-  max-width: 1000px;
+  max-width: 1200px;
   width: 100%;
-}
\ No newline at end of file
+  margin: 0 auto;
+  padding: 0 min(2rem, 4vw);
+}
+
+@media (max-width: 768px) {
+  .app-container {
+    padding: 0 1rem;
+  }
+}