SetGUITransparency (INV, 100); //Totally invisible
Wait (1);
SetGUITransparency (INV, 90);
Wait (1);
// ..etc
SetGUITransparency (INV, 10);
Wait (1);
SetGUITransparency (INV, 0); // Fully visible
//int vis = 100; // declared somewhere else
while (vis > 0) {
SetGUITransparency (INV, vis);
vis -= 10;
Wait (1);
}