The emulator needs system ROM files. Please drag the missing files into the empty chip sockets. Or just touch or click the sockets.

most settings are permanent and will be saved to your local browser storage

cut out sprite layers (stencil) system roms ...

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This is the place where you can create app or game specific customized overlay buttons with free positioning ...
app scope
compose an action sequence, for example

• loop5{j2fire1=>120ms=>j2fire0=>90ms} which will shoot 5 times
• or a literal action enclosed in single quotes e.g. 'load"$",8'
• or key combos e.g. CTRL+W  pressControlLeft=>W=>releaseControlLeft
• or A=>await_action_button_released=>B
for A on button down and B on button up in locked mode (see settings)
• for more complex tasks you can also choose to add a javascript ...

actionscript

actionscript javascript

live complete

add

javascript

special key

joyport1 action

joyport2 action

timer action

system action

... after created you can change the position of the action button by dragging ... when clicking the action button with a long press it goes into edit mode which takes you right back to here ...