I made this single player CCG in HTML5, which you can play for free on kongregate. You are protecting a city made of tiles like banks and gunposts which can be attacked at random and destroyed by a monster. But you can gain money each turn (like in hearthstone) which lets you cast cards onto your city tiles or cards that command your giant mech to attack the monster.
All 52 distinct cards start off unlocked and you can design your own decks (or use one of 3 preconstructed decks I included in the game). The game has been up on kongregate for 2-3 days now but hasn’t been rated enough times by registered users for me to be able to see the average rating. You can play on normal or hard mode; there’s enough RNG in the game that you just need a good deck and some luck to beat it on hard, I’ve done it with two completely different decks so far