OD3WUB5B7ZQDWBWAYNN6INLWIT5Z7UGMIPCLULS4UX5FVXWHTEZQC
EBRL7VKRBTW7VNIADHVR7UNP5L24S74TTWRWYKNT2OH4K4ZRAIOQC
66S4D75QXKMH6B27JC6X5SAA4QCUAAE6QYRQX2RDYKJW4ISNQMSQC
N2NUGNN4E37TNLC6JZE4H4HKJZPNVBV4VYTLXW57AP5BOU4ZK7LQC
THJX6RCJEMADQ3O6UOXA5DMGVGHMVKZHG4U7IUEV5E75FC3XRHXQC
RHARLLIQPGKVXNYQSIAZWILUI6F3CWMZ3ABJVI52IC3RBRSWPR5AC
LXFHXL2NSH7KLRNNN66OPNSU4DXZ6UU2CUPXUHCFEISDB6BY7KDAC
OTIBCAUJ3KDQJLVDN3A536DLZGNRYMGJLORZVR3WLCGXGO6UGO6AC
VUAAYL6XGFPYE6WNQ3HQTZI7K7K27DQ3LMJ5NJDGDPCIS75347SQC
Y5XAFGMWTCVHNO4XQAHN7J2SAMNALDM7TCDGJ56HFRQCTHQ4SQ6AC
M7UODV5HDRZKAS3BKGLNU5Z5HM4KZDM4QIB2S3E6S7NAWGJY3MJAC
5GHT3LUX5SHCBV5ZPHCZM5H56BV5IVY7MXBDEO2NZKSMSL24PZOAC
* `on.mouse_focus(in_focus)` -- called when the mouse pointer moves on or off
the app window. `in_focus` will be `true` when mouse comes within the window
area, and `false` when it goes off.
(Based on [LÖVE](https://love2d.org/wiki/love.mousefocus).)