Attacking and Taking Damage

Attacking
Mike has a number of weapons available to him throughout his adventure. While he primarily uses one of his Yo-yos, he also has access to a wide variety of other weapons, from Baseball Bat s to Ray gun s. Weapons are equipped with either the D-Pad when the game is paused with Start, or they can be cycled through with the Select button, right to left. Pressing B uses the selected weapon. Mike will use the weapon in the direction in which he is facing, not the direction he is moving (for more information, see: Basic Movement) Each weapon has an attack duration, which freezes Mike in that direction and blocks further input until that duration is complete. Most weapons attack duration will automatically end when the attack hits an enemy, with projectile weapons having varying rules based on the weapon. Attacking in a different direction than Mike is currently moving will introduce 16 frames of movement lag. This lag can be cancelled, which is discussed more in depth at Dungeon Lag Cancellation.

Taking Damage
When Mike contacts an enemy, under most cases, he takes damage. When this happens, he takes a varying amount of damage (.5 heart all the way to instant death for bosses), and then (if he is still alive) he freezes for 16 frames, and then gains [INSERT NUMBER HERE] invincibility frames (i-frames). During these i-frames, Mike cannot take any damage, or be insta-killed by boss contact. The most notable example of this is how C-Serpent is skipped (See Dungeon 1-1), but this can be used in many other places to varying effect.

Health
Mike has starts off with 3 hearts of health, which increases throughout the game. This number is supposed to be increased using the Big Heart items scattered through the world map, but loading a new chapter starts Mike with the full upgrades of the previous chapter, including health upgrades. Each heart actually denotes 2 hit points, and as such Mike can take half-hearts of damage. Hearts can be recovered through fixed heart pickups (double or quadruple), or through enemy drops. Enemies can either drop single hearts (very rare), or stars (more common), 5 of which recover one full heart.

Coin Flip
Like many NES games, StarTropics does not process collision on every frame. Instead, it processes collision on every other frame. This can have a number of effects, notably determining whether Mike's Yo-yo can deal damage at the last pixel of it's range. This can lead to enemies seeming to randomly be damaged by certain attacks, so bear this in mind, and always have backup strategies ready for if an attack fails.