Starmaps is an action-adventure game heavily inspired by the The Legend of Zelda series, and is intended to take on the role of the more linear, dungeon based 3D titles from that series while games like Breath of the Wild become open-world. The player controls Estrella, a young courier girl who seeks to undo the damage a previous mythical hero did upon the world of Almyria by going against fate. The action of the game is generally split between the mostly open outside world and the linear but intricate dungeons.
Exploring is mostly open, as almost the entire world is open, other than a few limiting factors. The Thunder that covers the exterior of the world damages the player as they enter it and remain inside, blocking all but the lightest progression outside of its bubble, and much of the world starts out submerged. Thus, completing the dungeons to remove parts of these afflictions is key to opening up more of the world. Additionally, completing dungeons can earn Estrella new items that she can use to explore, although they are usually optional.
The world has a fully featured day and night system, with NPCs having complex behaviours based on a schedule similar to Majora's Mask. Each NPC has multiple interactions and chains of quests to complete for them that can open up interactions with NPCs; completing these quests can give various rewards, including lowering shop prices in that region. The day/night cycle also determines exploration, as it is actually easier to explore at night; undead creatures will spawn during the day at any place that the light tooches.
The world of Almyria has been impacted by four devastating forces that are enacted on it via the four main dungeons. The entire map is surrounded by a circular wall of thunderclouds that cause continuous damage while inside them, stopping Estrella from travelling too far outside into the Thunder and completely blocking off many areas; the water level has raised so as to flood the entire region, submerging entire areas that can only be accessed after dropping it later; dangerous undead forces rise from the ground anywhere the sun touches, and beacons of light summon even more; and hailstorms often roll in from the north, covering entire areas in frost and blocking off areas with ice.
The main dungeons that power these forces are not intended to be tackled all at once; instead, Estrella is able to enter them all almost immediately as she reaches them, but will likely only be strong enough to tackle one or two floors, and can return later to take on the rest. Each dungeon is made up of four levels, and completing them will gradually reduce the corresponding dungeon's effect on the world; for example, tackling one level of the Fortress of Energy will expand the eye of the Thunder, allowing Estrella to explore more of the world.
Each main dungeon has an item that can be unlocked by reaching the end of the second level, while the two optional dungeons instead have upgrades to existing items. Each item is required to clear the rest of the dungeon, and can also be used in each of the other dungeons to make them easier, although they are never required for the other dungeons. Additionally, the two optional dungeons each require one of the other items to access them, as said items' upgrades are needed to beat the corresponding dungeon.
Although the game is technically considered beaten by finishing all four main dungeons, as their curses will be lifted from Almyria, there will be one additional final dungeon that can only be accessed after all the main dungeons are finished which uses all of their items and is more difficult than the rest.
The eponymous feature of game is the StarMap system. The ancient hero traveled across Almyria many centuries prior and left behind StarSpots where he formed strong memories, forming a web of connections between key locations. Upon identifying a StarSpot, Estrella will be able to see a memory of what that location was like in the past, before earning StarPoints and unlocking connections to other StarSpots. Following the connections from a StarSpot will lead her to another, encouraging her to explore along certain critical paths but not requiring it. The completed StarSpots will reveal stars in the night sky that represent those memories, which can be seen again and tracked from the menu.
StarPoints are earned by finding StarSpots; some StarSpots immediately reward the points, while others require more exploration, using the memory as a hint. StarPoints serve as the primary way of increasing Estrella's abilities, as collecting them will slowly progress her towards her next Level increase. Each Level will provide its own bonus, such as increasing maximum HP or damage output; because this is the way for players to gain these bonuses, collectibles like the Heart Containers from The Legend of Zelda do not appear. StarSpots and StarPoints are also the main optional collectible in dungeons, where they can also give additionally guidance to the player if help is needed.