Experience

Traditional grindy "experience" that goes up to the hundreds of thousands is replaced in this game with estimating encounter difficulties and rewarding the party with slices of levels accordingly. Quests and fights are divided into trivial, easy, risky, elite and suicidal depending on their difficulty compared to the party's current abilities. A basic "experience point" is always 1/10th of a level.

Every level up increases a character's health pool by CON modifier + racial hit die.

A trivial encounter is a distraction vastly below the player's level. It takes no thought or struggle and offers nothing of value. An enemy over 3 levels below the party, for example.

An easy encounter takes some effort or reason, but is otherwise non-threatening to the party provided they work hard. One enemy equal to or 3 levels above the party or a swarm of enemies up to 3 levels below theirs, for example.

A risky encounter is dangerous, but still feasible with enough strategy. Eg: multiple enemies at once equal or up to 3 levels above the party, or one creature higher than 3 levels above the party offer 2 experience points. Challenging but simple side quests that don't require one or two regions worth of travel offer 2 experience points once completed.

An elite encounter could reasonably take an entire session, such as a final dungeon boss, an intermediary campaign boss, or finishing a full multi-point traveling side quest. This awards the party half a level each.

A suicidal encounter, at the DM's discretion, is something vastly overleveled for the party's current ability (5+ levels). This includes dungeons or side quests planned for several levels later, and for balance purposes finishing one entire campaign counts as this. If the party manages to succeed, they are awarded 1 full level.