Noticed some players are getting stuck, so I’m posting a quick walkthrough in the comments.
If you’d rather avoid spoilers, please skip it!
If you hit a tree while holding a rock, a log will spawn.
Breaking the log gives you 2 wooden sticks.
You can combine 1 wooden stick and 1 rock to craft a campfire.
Hunt a rabbit and cook it on the campfire to get cooked meat.
Then, combine the bone from the cooked meat with a wooden stick to craft a bow.
Hold and release the E key to shoot the bow.
After that, defeat the primitive man who spawns with a spear to obtain a pickaxe.
Once you have the pickaxe, rocks will start to spawn.
Run into a rock while holding the pickaxe to mine it.
Mining rocks gives you stones and copper.
Put stones into the campfire to create a furnace.
You can smelt copper in the furnace to craft copper armor.
After equipping the copper armor, an enemy with a bow will appear.
The copper armor deflects arrows.
Defeating the archer spawns iron ore, which you can mine to obtain iron.
Smelt the iron in the furnace to craft a gear.
Combine the gear and a bow to make a crossbow.
The crossbow is a rapid-fire weapon—hold E to shoot continuously.
Once you've crafted the crossbow, a mounted enemy will appear.
Be careful—the horse-riding enemy moves fast!
Defeating them drops gunpowder.
Combine gunpowder with the crossbow to craft a musket.
After crafting the musket, four enemies in copper armor will spawn.
The musket can pierce through their armor.
Once you defeat them, a wrench will drop from the sky.
Combine the wrench and a furnace to build a steam engine.
Insert the musket into the steam engine to craft a rifle.
After crafting the rifle, a swarm of enemies will appear.
Defeat them all!
Once cleared, a circuit board drops from the sky.
Combine it with the steam engine to craft a computer.
Insert the rifle into the computer to build a missile.
To use the missile, hold E to begin locking on, then release E to fire once locked.
After crafting the missile, a spaceship appears.
Defeat it to obtain an energy core.
Combine the energy core and the computer to build a time machine.