Montanha: Zero Day

Montanha: Zero Day is a cyberpunk side-scroller: the hero wears a jetpack and a hacking watch, fighting monsters through a neon city to take on RANSOM-TITAN, a ransomware-virus boss, all playable in the browser.

Three levels tell one story: in level one the hero rescues a companion frozen in a pod, only to walk into the boss trap and get captured; the next two levels switch to companions fighting back with a golden arm cannon and light-speed boots; in the end you smash the boss core, grab the decryption key and rescue the hero.

It is a web app that works offline too, and installs on a phone like a small app without staying online; the art is hand-drawn pixel style and the music is generated live by code, so there are no big audio files to download.

Note: on a phone you need to hold it sideways — holding it upright first shows a "please rotate" prompt; this is a one-person, one-day game and the author himself says he cannot guarantee it is bug-free, so do not judge it by AAA standards.