To easily gain health and ammo, collect the health and ammo at a checkpoint and save the game. Leave the room, then load the checkpoint you just saved. The health and ammo will reappear at the checkpoint.
Save the game at a checkpoint. Exit the room, pause game play, and select the "Load Checkpoint" option. You will keep your current health and ammunition and restart at the checkpoint where you can re-collect the health and ammo there. Repeat as desired.
-After the cutscene where Claire is taken away by the helicopter, go left back through the save room and out the other side to a cliff. Jump across the cliff to the platform and climb up to the other side, then continue left until you reach the jeep. While in front of the jeep, press B and you will enter the car and unlock the Achievement
-To get "Single", you don't have to wait until Claire gets captured in the helicopter. You can get "Single" after you've got the grenade ability and killed the first large spider boss. There is a path where you can jump over the cliff to the other cliff (from RIGHT to LEFT) at the left (the starting point) towards you jeep. (Press "B" when you you meet the jeep at the background.)
Reach the following levels to unlock the corresponding bonuses:
LEVEL - BONUS Level 20 - A full map that reveals the location of all items, weapons, and other items, Level 10 - Health boost Level 30 - Infinite foam ammunition Level 40 - Infinite grenade ammunition Level 50 - Infinite rocket ammunition
ACHIEVEMENT - HOW TO UNLOCK Let's Get Punchy (15 points) - Melee 5 soldiers. Bomba Punter (20 points) - Punt 20 Bombas. My Head A-Splode (20 points) - Get 50 head shots. Make 'Em Scream (20 points) - Get 100 soldiers to scream. To Kill a Blackbird (15 points) - Destroy the helicopter attacking the Vice President. Look Out! (5 points) - Kill a soldier with a Bomba. Walkin' on Water (5 points) - Make it from one end of lake to the other in hyper-Speed. Hero (50 points) - Beat the game on any difficulty setting. Completionist (20 points) - Beat the game with 100% of the items. Minimalist (10 points) - Beat the game with less than 13% of the items. Proven Grounds (10 points) - Beat the Proving Grounds. Serious Complex (10 points) - Reach experience level 50.