There are lot of Battle City clones exist in this world. This one is Pico-8 port, made by me just for fun.
Changelog:
Version 1.0:

First 'stable' release (moved from 'work in progress' to 'cartridges' as it's almost finished, maybe later i'll add some new features like level constructor, but not sure about it).
Moved Game Over screen after score calculation, like in original NES version
Added Hi-Score screen after Game Over screen (if player beat high-score)
Changed palette, now it uses 'secret' Pico-8 palette for bricks. Can be toggled through menu if palette doesn't work for some reason.

Version 0.2:

Fixed lot of bugs.
Normal music and sfx. Some sfx (tanks explosions) are not so good because NES noise channel differs from Pico noise and cannot be made with Pico.
Different role for shooting buttons: rapid and single.
Level selection at the start, score screen at the and of each stage.
Hard mode after stage 70, enemy tanks have all advantages of basic 4 tank types.

Version 0.1:

Core game for 1 or 2 players
Original 35 levels (after level 35 they start to repeat like in original game)
Random mode, which generates every level from random nine pieces of existing levels
Progress automatically saves between levels, you can reset cart and continue later, but erases on gameover, like in rogue-like games. May be useful on random mode, if generated level is impossible.

To do:

Level editor
Maybe implement some features from chinese '1990 tank' hack
Maybe storyline between levels
Feature requests are welcome