A draft theme using Bulma Css 
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Feedbacks are welcome 
Asmbb Bulma Theme
Theme on Mobile device 
Oh! It really looks much better this way!
But the red logo above is actually not suitable for this theme...
Thanks for the feedback, it need improve and optimize a lot 
More fix
Great! But how are you changing the dark/light themes? I see, it is a single theme named "bulma2".
Bulma is a light theme only as in screenshot. Bulma2 is a customized theme that can change UI by changing the pre-made bulma CSS file url (Bulma Watch) . I still don't know how to change theme on-the-fly with it 
The biggest problem with this approach is that the emoticon images are not changed on the dark theme. The emoticons are defined through the symlink templates/THEME_NAME/_images/emoticons (and chatemoticons for the chat). So they can't be changed by JS or CSS tricks.
One possible solution is to use SVG emoticons (because of transparency), that are designed in a way to be suitable both for the light and dark themes.
Thanks for the suggestion, AsmBB has the change theme function so I think a dedicated dark theme is better, it doesn't need to be all-in-one theme,thanks AsmBB