partial modifier_keys
xkb_symbols "rocket" {
    key <TAB>  {[    BackSpace,  Escape,                  BackSpace,              BackSpace ]};
    key <CAPS> {[        space,  space,                       space,           nobreakspace ]};
    key <LCTL> {[          Tab,  ISO_Left_Tab,                  Tab,           ISO_Left_Tab ]};
    key <BKSL> {[          bar,  backslash,                     bar,              backslash ]};
    key <RTRN> {[        space,  space,                       space,           nobreakspace ]};
    key <RCTL> {[       Return,  Return,                     Return,                 Return ]};
    key <SPCE> {[    Control_L,  Control_R,               Control_L,              Control_R ]};
};