I am going to see if I can do this one in Batari Basic.
The premise is to see how long you can hold of the pass with 300 Spartans against unlimited attackers at the pass of Thermopylae. It will be maybe 6 rows wide and 4 rows deep to form the Phalanx, and as you lose Spartans from the approaching hoard, you deploy new Spartans from the back to keep the 4 ranks filled. The phalanx is strongest 4 ranks deep, and will die off much slower. The odds of losing a Spartan varies, but there will always be a chance of losing one, so it will be impossible to play forever, and your score will be either how many you kill, or how long you survive.
I have some details in my head, I need to mock up a screen and gameplay. You will be Leonidas giving orders, and I plan to use keyboard controllers to decide where to order replacement Spartans, to pick which rank they go to.
If it works out as fun, I was hoping for between level rounds where you pick blocks representing dead bodies to build a wall.