Is bubble app paid?

Could you please clarify for me if the bubble app requires payment? I'm considering downloading it but I'm not sure if it's a free service or if there are any subscription fees involved. Is it a one-time purchase, or do you have to pay periodically to access its features? Additionally, are there any hidden costs or in-app purchases that I should be aware of? It would be helpful to know if there's a free version available with limited functionality or if the full version is paid only. Thank you for your assistance in clarifying this matter.