The colony grows by working out its own needs. For example, if there is enough food the ants will build more granaries, and if too many ants die they will build more graveyards. There are a few controls, like how often floods come and where the queen moves, but you can leave those to the game.
Egg → larva → pupa → worker. The queen lays, and nurses carry each young ant to the right nursery as it grows. A larva only grows while it's being fed.
Jobs. Workers dig, haul spoil up to the mound or down to the refuse pit, harvest seeds, husk them, feed larvae, tend the queen, help new workers hatch and bury the dead. Each ant picks up whatever needs doing.
Growing up. A new worker is pale for a while (a callow). In a big colony the young stay inside nursing and the old go out to forage. Ants slow down near the end of their lives, and the dead are carried down to a graveyard.
Growth. The colony keeps growing while food keeps coming in, up to the population cap in Settings.
The queen is dead. If every worker dies, the queen can't carry on alone: she lays no more eggs, the brood stops hatching, and soon after she dies too. The screen greys out, and ⟲ starts over.
Plants. Plants grow on the surface and ripen seed heads. Harvesters climb the stems to cut the seeds. Stripped plants regrow or wilt.
Rain. Now and then it rains. Rain darkens and soaks the ground, washes the mound flatter, and sends ants underground until it stops. A few new plants sprout afterwards.
Deluge. A flash flood that pours down the entrances and can drown the nest. The ☂ tag (or D) calls one, or set how often they arrive in Settings. They're off by default.
Centipedes. A hunter ten ants long that comes in over the surface and goes for the nurseries. The ants that meet it raise the alarm and it spreads through the nest. About a third of the alarmed ants fight (they flush red); the rest carry on with their work and steer round it. Defenders clamp onto its body, slowing and wounding it, and it thrashes to throw them off. Hurt badly enough it runs, and it can die in the nest. The queen is always safe. The centipede tag (or C) calls one, or set how often they come in Settings. They're off by default.
Collapses. Where rain or a flood has soaked the ground above a room, or washed the sand out from under it, a stretch of tunnel or chamber can give way, burying and blocking ants.
Water. Hold V and move the mouse to pour water anywhere. B drains it all away.
Water. Open ⋯ and tap the drop for pour mode, then touch the world to pour water there. Tap the drop again to stop. The grate beside it drains it all away.
This colony isn't saved.