In DOOM, the main objectives involve navigating through various levels, defeating enemies, and ultimately reaching the end of each level, usually against a boss. Players must collect weapons, power-ups, and secrets to enhance their abilities.

To use weapons effectively in DOOM, familiarize yourself with their strengths and weaknesses. Prioritize using weapons suited for specific enemy types and reload often. Experiment with different combinations to maximize damage output against tougher foes.

Glory kills are special finishing moves in DOOM that provide health boosts. To perform a glory kill, weaken an enemy until they flash, then approach and press the interact button to execute the kill, gaining health and ammo.

In DOOM, players can upgrade their character through a skill tree offering various enhancements. To access this, follow these steps: 1. Pause the game. 2. Go to the upgrade menu. 3. Spend points earned from combat. 4. Choose desired upgrades to enhance abilities.

To defeat tougher enemies in DOOM, keep moving to avoid attacks, use cover, and utilize the environment strategically. Learn enemy attack patterns, prioritize weak points, and switch between weapons based on enemy vulnerabilities for the most effective combat approach.