Gameplay
Each level of Oasis consists of a single screen with a 10x10 grid of randomly-generated terrain. Initially the map is covered with fog of war, but the player may remove the fog from tiles by clicking on them. Each click reveals a single tile and takes a turn, 85 turns are available for each level. The eponymous oasis covers several squares of each level and lying in a random oasis tile is the obelisk which contains the level's glyph of power. The primary goal is to find the glyph and protect it from barbarians who attack after the 85th turn from tiles marked by blue cairns. To stop the barbarians from destroying the glyph the player must find cities and use them to mount a defense. If the player finds and defends 12 glyphs he or she wins the game.
Layered on top of the basic gameplay are eight scenarios. Each scenario presents a narrative about a different land and the story of a different leader rising to power. In the first scenario players assume the role of an Egyptian noble, the son of the murdered Falcon King, who wishes to rebuild the nation and disperse the fog that has plunged the nation into chaos since his father's murder. Each scenario has its own theme, and each level within a scenario is distinguished by a mix of special gameplay elements related to the theme, such as barbarian strongholds, jungles, islands, plagues, and others.
Most tiles give the player a number of followers when revealed. Followers are a resource; the player may spend them to build roads or he may send them to work in the mines. Both activities also cost a turn. Cities connected by roads gradually grow whereas followers working in mines research combat technology. Both benefits accrue over time, which encourages early investments in mines and roads. Turns can also be spent searching cities which reveals either treasures or advisors. Most treasures provide an attack bonus to the population in that city. When found, advisors pledge to join the player if enough cities survive the barbarian attack. Advisors grant bonuses to the player and substantially alter playing strategy.
With 100 tiles and just 85 turns the player cannot hope to uncover every tile. He or she knows however that the map is not entirely random. Certain features are present on every or nearly every map: the oasis, cairns, cities, the nomad camp, and mountains. There are clues to finding each feature: the oasis and cairns always appear on the edge, cities are surrounded on all eight sides by crop tiles, the nomad camp appears in the largest block of desert, mountains can be seen from 1 square away and mountain ranges are either 'U' shaped, 'S' shaped, or stretch vertically across the map. As an additional clue to finding cities, the number of cities touching a crop tile is the number of followers gained when the tile is uncovered. This sometimes results in being able to find cities in fewer clicks by solving a small Minesweeper-like puzzle.
The central tension of the game comes from making trade offs. The player always has more avenues to improve his/her position than he/she has time and resources to pursue them, especially when it comes to spending limited turns and followers. For example, spending turns on exploration provides followers and strategic information, but it delays roads and technology which benefit from early investments. Connecting a far away city could result in net population growth, but it may take valuable time away from searching for a crucial treasure or cairn. Searching the oasis costs turns and gives no immediate value, but it boosts your score and leads to bonus levels which often result in a free glyph and advisor.
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