The game has five playable characters: Legolas, Gandalf, Gimli, Aragorn, and Frodo Baggins. Gandalf is chosen for this movie.
The differences between the characters are quite minor: almost everything is the same for each character, except for the projectiles that they fire, and associated upgrades. All characters have 4 different upgrade levels for their weapons, with later upgrades generally manifesting in different forms of spread shots.
There are a few universal mechanics for each character's upgrades:
- Each projectile has a firing delay before another projectile can be fired. This is 16 frames for the first upgrade level, 19 frames for the second, 22 frames for the third, and 25 frames for the fourth.
- All projectiles from the first or second upgrade level do 1 damage to enemies. All projectiles from the third or fourth upgrade level do 2 damage.
As a reference, bosses have just 4 frames of invincibility per hit, which means that for optimization purposes, the biggest limiting factor for damaging bosses is not the invincibility time, but rather the firing delay between projectiles. However, those 4 frames of invincibility do mean that it's not possible to do multi-hits with projectiles that reach the enemy at the same time. This renders most attacks like spread shots useless, as it's simply not possible most of the time to hit different spread shots with enough time in-between.
So, enter Gandalf. With upgrades, his projectile fires a secondary fireball. Regardless of initial firing direction, this fireball will be launched in the direction of an enemy upon firing (precisely which enemy is a bit wonky, but can be manipulated reasonably enough). It also moves half as fast as Gandalf's normal projectiles. This means that it can be used to reliably double-hit just about every boss in the game, which gives Gandalf a significant edge over all the other characters in terms of speed.
Since the third and fourth projectile upgrades both do 2 damage per hit, and the fourth upgrade takes a few frames longer to fire, it's actually optimal most of the time to stick to the third projectile upgrade. This is used for the majority of bosses in the game. The fourth upgrade's only advantage with Gandalf is that it will fire two fireballs sideways, which can be useful sometimes.
Besides their projectiles, the characters also have a melee attack. This attack deflects projectiles, and one-hit kills almost any regular unit in the game, but does not affect bosses at all. This is universal for all characters. In stages it is sometimes useful because the character has to stand still for the duration of the animation, but sometimes it is still useful anyway.
All characters also have a special super-move that clears the screen of all regular enemies, but it cannot be used during boss fights, is mostly unnecessary for regular enemies, and wastes a ton of time, so it is never seen in this movie.
The most important aspect of optimization in this game is actually not so much the movement of the player, as it is the movement of the camera. Obviously the two are tied together, but advancing areas or spawning bosses generally depends on the position of the camera, so making sure the camera does not lag behind at any point is of utmost importance.
Conveniently, it's rather easy to get ahead of the camera, especially when taking a turn towards a new area. If the character is ahead of the camera, the camera will keep scrolling at a consistent 2px/f pace as long as the character is facing forward or diagonally forward (with less wiggle room if facing diagonal), even if the character isn't actually moving.
In the first few levels it's most obvious that the pace of the run is more dictated by the camera than by the player character, but later levels with more enemies make it significantly harder to move on unimpeded, so there still remain lots of challenges along the way.
Every world (except world 7) has one boss battle, which appears at the end of the last stage. World 7 also has two boss battles in the middle of its stage.
All bosses have 100 HP, 4 frames of invincibility on hit, and the projectiles we use against them deal 2 damage per hit. It's possible to deal damage before the boss dialogue starts