Unlock Endless after your first win
The official 1.3 announcement says Endless unlocks after winning the game at least once. That rule was reviewed against later official announcements through 1.6, but it was not reproduced in a current client during this research.
This page does not prescribe a current menu path because the reviewed source establishes the unlock condition rather than every present-day button label.

What stops being granted after level 25
Endless can continue past level 25, but the official rule stops granting several new resources after that point. This does not remove yellow skulls already held or prove that an existing effect can no longer restore a reroll.
Hand upgrades follow a separate limit: the game stops offering them once every hand is fully upgraded. The source does not say that all hands become maxed exactly at level 25.
| Reward or upgrade | Endless rule |
|---|---|
| New yellow skulls | No longer granted after level 25 |
| Extra hands | No longer granted after level 25 |
| Extra rerolls | No longer granted after level 25 |
| Hand upgrades | Stop after all hands are maxed |
How Endless progress is measured
Endless has no victory endpoint. Its separate leaderboard ranks runs by the level reached rather than total score, so a useful run record starts with the final level.
Challenges cannot be used or unlocked in Endless, and only some achievements are restricted. A complete restricted-achievement list, routes beyond level 34, high-level builds, and a maximum reachable level remain unverified.
