Bubble Tanks Tower Defense is an open path tower defense game with the following specifics:
>you have typically have 20 lives, if 20 enemies get to the other side, you lose
>killing enemies almost always gives you bubble(s), which are the game's only currency
>enemy waves can intentionally be triggered early by the player
>before wave 1, you can take as long as you want to place towers; afterwards, enemy waves come on a timer
>the game can be paused, but you can't do anything while its paused
>no tower research; you can go straight to max lvl towers at the start of the game if you can afford the upgrades
>towers can be upgraded, first pic related
>11 enemy types
>over 60 different levels to play
>no temporary tower upgrades exist
>tower AI cannot be configured, not even for all of them at once
>no friendly creatures exist; its just your towers versus the enemies
>towers are the only way to hurt your enemies
>towers cannot be broken or killed, with the exception of the suicide bomber tower; the EMP enemy can disable towers for a few seconds upon death
>towers can be sold or placed while enemies are on the map, allowing for a technique called juggling, second pic related; several or more levels pretty much require juggling to win
third pic related is a gameplay screenshot