Not bad for your first game! The art style was cute. It was cool how you made the CPU's face and dialogue get angrier or happier depending on how you did. You could probably even add more of it or additional "stages" of reactions and it would go a long way.
The game was lacking a bit in difficulty though. One of the reasons, I feel, is the fact that Player 1 makes the first move each time, and another is that the grid is only 3x3. I suppose letting the CPU cheat is a nice way to spice things up. If you wanted to add more challenge to the game, you could consider randomizing who goes first each round, or adding an option to play on a bigger grid. This would also help avoid too many games ending in a Draw.
With games as universal and basic as Tic Tac Toe, it's important to have something that makes yours stand out from the rest, and the addition of unlockable bonus artwork for beating the CPU based on certain conditions was a good decision. It definitely kept me playing this for longer than I would have otherwise. The sound effects fit well, but some basic looped music would have been nice to round out the entire package.
Keep up the good work! You chose a great game for your very first project, and hopefully it helped you learn a lot about coding and game making. Don't be afraid to try something a little more complex for your next project, but don't bite off more than you can chew!