Lot of visual improvements.

src/app/active-list-tasks/task-display/task-display.component.html

@@ -5,8 +5,9 @@
         <div class="input-container">
             <input type="text" [formControl]="titleControl" />
         </div>
-        <button mat-button type="button" class="expand" (click)="expand()">
-            <mat-icon>expand_more</mat-icon>
+        <button type="button" class="expand icon" (click)="expand()" matRipple>
+            <mat-icon *ngIf="!isExpanded">expand_more</mat-icon>
+            <mat-icon *ngIf="isExpanded">expand_less</mat-icon>
         </button>
     </div>
     <div [ngClass]="getExpendedClass()">
@@ -18,10 +19,10 @@
                 <textarea id="description"></textarea>
             </div>
             <div class="actions">
-                <button matTooltip="Définir une alerte dans X minutes">
+                <button class="icon raised" matRipple matTooltip="Définir une alerte dans X minutes">
                     <mat-icon>update</mat-icon>
                 </button>
-                <button>
+                <button class="icon raised alert" matRipple>
                     <mat-icon>delete</mat-icon>
                 </button>
             </div>