The file open button will be enabled once the UI initialized.
Read file:
After loading the game,may need to click the white space of webpage to obtain keyboard focus. 
            Key mappings:
            g.cfg.PadDef[0].KeyDef[DKEY_SELECT].Key = SDLK_c;
            g.cfg.PadDef[0].KeyDef[DKEY_START].Key = SDLK_v;
            g.cfg.PadDef[0].KeyDef[DKEY_UP].Key = SDLK_UP;
            g.cfg.PadDef[0].KeyDef[DKEY_RIGHT].Key = SDLK_RIGHT;
            g.cfg.PadDef[0].KeyDef[DKEY_DOWN].Key = SDLK_DOWN;
            g.cfg.PadDef[0].KeyDef[DKEY_LEFT].Key = SDLK_LEFT;
            g.cfg.PadDef[0].KeyDef[DKEY_L2].Key = SDLK_e;
            g.cfg.PadDef[0].KeyDef[DKEY_R2].Key = SDLK_t;
            g.cfg.PadDef[0].KeyDef[DKEY_L1].Key = SDLK_w;
            g.cfg.PadDef[0].KeyDef[DKEY_R1].Key = SDLK_r;
            g.cfg.PadDef[0].KeyDef[DKEY_TRIANGLE].Key = SDLK_d;
            g.cfg.PadDef[0].KeyDef[DKEY_CIRCLE].Key = SDLK_x;
            g.cfg.PadDef[0].KeyDef[DKEY_CROSS].Key = SDLK_z;
            g.cfg.PadDef[0].KeyDef[DKEY_SQUARE].Key = SDLK_s;
XBox Cotrollers also work, but currently only maps to chrome/windows.