Primal Quest is an osr stone age ttrpg with an easy to learn system, beautiful lurid red art, and a complete hexcrawl included.
The PDF 30 pages, and those 30 pages feel extremely meaty.
Lore-wise, Primal Quest takes place in a world where early humans and dinosaurs co-inhabit the earth. Fire and flint are new technologies. Humans congregate in small bands. And the world is violent and strange.
System-wise, Primal Quest uses sort of a weird core mechanic. To resolve a check, you roll a pool of positive dice and a pool of negative dice, count only the highest, subtract the highest negative from the highest positive, and then compare the remainder + Attribute against a Target Number. Dice are d6s, so as the pools get bigger, the odds of rolling a net 0 get higher. Rolling 6s on positive dice does generate a currency that lets you influence rolls and make them easier, but rolling 6s on negative dice generates a currency that lets the GM make your life harder. This feels to me like it's almost on the cusp of being diceless, but it's definitely a stable system and fiddling with the currencies feels fun.
Character creation is simple and solid. You have three attributes (body, heart, mind) and assign a small pool of points between them. You also define who your character is, what they care about, and what holds them back. Equipment is a little more complex, and you track torches, rope, food, water, etc, but carrying capacities are high and the penalty for going overburden isn't too onerous.
Trade is interesting, in that money is nearly unheard of so mostly you're bartering with resources, but the resource values for a lot of common stuff aren't defined. This kind of turns each exchange into an in-character assessment of whether the trade feels fair, which is flavorful and neat.
XP is pretty granular. You gain points often, simply by interacting with the game's systems, but you need a lot of points to buy advances.
Combat uses the same core dice system as the rest of the game, but also allows you to move forward and back in range bands.
Magic is relatively freeform---you combine a few keywords, tell the GM what you're trying to do, and the GM adjudicates the effect.
For GMs, there's quite a few resources in the book. There's a link to a safety toolkit at the start, there's advice on how to tailor your GMing to the system, there's reaction tables, rules for exploration and camping, and again there's a full hexcrawl scenario just waiting for you to run it.
The scenario, Mother's Vale, is beautifully mapped and has a nice balance between points of interest and empty tiles. The plot is very open-ended, but there's lots of trouble to get into and different communities to interact with, as well as a good helping of wild creatures to fight. If you like games like Skyrim and Fallout that just drop you into a huge sandbox and let you explore, you'll enjoy the feeling of this scenario.
Overall, Primal Quest Essentials is a great, meaty, lightweight game delightfully ahistorical stone age pulp. If you like old school games that experiment a bit with their mechanics, and especially if you like flinging spears and chanting fireballs at giant dinosaurs, give this a go.