Yes it's a browser related issue. I opened the game on Opera browser and it worked just fine. But there's a major glitch when you die at first try you cannot get any damage from the boss again and you stunlock the boss with 4-5 hits. I kill the first boss, it appears over and over again. I could only pass to the second boss once. Sometimes the movement controls gets glitched out, the directions are getting mixed up. You press up, character goes down, something like that.
I am sorry with starting off with the negative things but the game has too many bugs. Besides all that, game looks and feels very very good. The character design, boss design, artistic style, i really loved that all. Art style of the game feel somewhere between PS1 and PS2 which i really dig. I also love that you see the changed equipment on your character. Btw exchanging equipment mechanic is a very good idea and fits the jam perfectly but it only works cosmetically right now. In the controls section of your game page it says right mouse click is special button but nothing happend when right clicked.
To summarize my thoughts on your game, it is very strong visually and in terms of gameplay but i think you struggle a lot in the programming department which is one the most difficult aspects of game development and i struggle a lot on that aspect too. I appriciate the hard work and time you spent on this game. I think this is a great experience for your game development career. I hope you all reach to the point where you aim to reach. Good luck to all of you!