The graphics... my word. I can't believe you not only made them in a short game jam, but also SOLO. They look so professional and the scenes are so well picked. They just perfectly compliment the story. The audio certainly matches both the game's visual style and story. From a visual and stylistic perspective... just 11/10 beyond perfection. You should be very, very proud of yourself. :)
In regards to storytelling. First off, very clever interpretation of the theme. I loved how it also doubled as the two-sided theme/lesson of the story when the dragon related Mirta's being locked in with her brother to his own prison. Nice incorporation of deep subject matter too with the forgiveness aspect. And also all of the main ideas (story beats) were well thought out and fit together.
However, I do agree with the comments saying the story did drag at times, especially at the beginning... and I think there's a couple reasons.
With the beginning... it felt a bit overly expositional, especially in the scene where they are walking to the castle. And while I understand all this information is necessary to the story, it could probably be condensed a bit. But the other reason is that obtaining the crystal (while the reason for doing so is clearly explained) didn't feel like quite enough incentive to hook the player and get them through that exposition. Once the dragon came in, the plot definitely picked up, but before then... I feel like some kind of ticking clock... higher stakes, would get the tension really rolling and have the reader tearing through that exposition wondering what could have gotten things the way they are.
The other reason I felt the story dragged a bit is... it felt like the main plot points and the story developments were a little bit disconnected. While the story points themselves were wonderful, the parts in between didn't really feel like they were building to those points. The development kinda just meandered, describing the siblings' emotions of fear and argument, which made the story points kind of come out of nowhere.
For instance, I found it a little strange that Mirta just happened to find the book that happened to have her first spell, that she just happened to say, which just happened to be the spell she needed to talk to the dragon. That's a lot of coincidences. But! don't get me wrong! The idea of her discovering the spell to speak to the dragon is a great one. I just feel like the development sections could be used to set this up as a believable plot twist, and reveal more about Mirta's character. Just little moments that show her skill at communicating... her compassion... and how it annoys her brother.
Like, just as a random example, maybe while fleeing from the dragon, Mirta uses the last of their rations to feed some hungry mice in the castle. She understands what they want, without words (hinting at communication/compassion) and the player will be able to see that as her brother yells at her and she defends them. That way, when the communication spell happens (perhaps with the help of an animal in the book? a bug eating away at the pages? a moth?) the player knows without a doubt... oh yeah... she's the one.
Sorry that got a little long winded! Hopefully that makes sense! Again just to reiterate, the story on its own is pretty good, but if you were to go back and to develop it more, I think expanding on these development sections to really tap into character and set up will really take the story to a whole new level.
Also a brief note on dialog. It's very good! But I feel like it could be a little more expressive towards more intense situations. In terms of word choice/tone, Fedro panicking felt exactly like Fedro talking normally. More words to show intensity could really show that panic, and maybe hint at an uglier side of Fedro while he was talking! Aside from that though, great job with the dialog. My teammates and I read the entire game out loud with a lil bit of our impromptu voice acting and we had so much fun with it. I had a blast playing the dragon.
Really well done with this over all. If you do more with this game, I can't wait to see the direction it goes.
-Sasha