Battlecards game is known also as "War" and is probably one of the oldest known card games. When I was a kid, I was playing a variation called "nälkä" (translated as word "hunger" in English).
The objective of the Battlecards game is to win all cards from opponent. This variation is one player game, so the opponent is always your mobile phone or tablet.
There are two modes in this cards battle game: 1) Normal game mode, no time-limit: Can last very, very long time 2) Quick game mode, 2 minutes time-limit: If you are in hurry, but want to take short game
The deck is shuffled and divided evenly among the players. On each round both players reveal the top card of their deck, and the player with the higher card takes both of the cards played and moves them to the bottom of his stack. Aces are high, and suits are ignored.
If the two cards played are of equal value, then there is a "battle". Both players place the next card of their pile to the table. If topmost cards are still equal, battle continues with another set of cards. Battle will continue as long as either player has higher topmost card than the other one (or player runs out of cards on his/her deck). Winner gets all the cards that were on the table.