There are six symbols in the game: → (Red symbol)
↓ (Blue symbol)
Λ (Green symbol)
V (Yellow symbol) ֍(Lightning - clears one symbol off each ghost on screen and used at the end of the final boss sequence) Note I can't find a Unicode character for lightning but you know what it looks like. ♥ (Heart - restores one heart)

Every level has a set of waves. The next wave appears when all the ghosts in the current wave are dead. However, some waves have timings so ghosts at a certain time - there's no way to speed this up. (a quite clear example of this is in Stage 2 before the boss) Therefore, you should focus on the last ghost(s) of a wave to get a good time. As general advice, you should just spam the symbol that comes next (you can look at this guide) and then read the rest.

The first ghost(s) in a wave is named Ghost 0.0s. If ghost(s) comes at a set time after these first ghost(s), it will be named after their respective times (e.g. Ghost 0.5s, Ghost 1.0s). These times are rounded to the nearest 1/10s due to awkward 30FPS recording. After you clear a wave, it takes 1.7±1.0s for the ghost(s) of the next wave to appear, whose level depends on certain stages, being hit by the last ghost, and if there is an upcoming boss.

I also recommend you play the game several times before reading this - that way you don't have to look at the reference every step of the way.

[Level 2]

Wave 1 Ghost 0.0s: →→ Ghost 0.0s: ↓→ Ghost 0.0s: Λ→ Ghost 0.0s: V→ Ghost 0.0s: ֍ Strategy: ֍→

Wave 2 Ghost 0.0s: →Λ Ghost 0.0s: ↓→ Ghost 0.0s: ΛV Ghost 0.0s: V↓ Ghost 2.0s: →Λ Ghost 2.0s: ↓→ Ghost 2.0s: ΛV Ghost 2.0s: V↓ Ghost 3.0s: ֍ Strategy: →↓ΛV then →↓ΛV֍. Note second ghosts are the same as the first.

Wave 3 Ghost 0.0s: → Ghost 0.0s: → Ghost 0.0s: ↓ Ghost 0.0s: ↓ Ghost 0.0s: ↓ Ghost 2.0s: Λ→→ Ghost 2.0s: V→→ Ghost 2.0s: Λ→↓ Ghost 2.0s: Λ→↓ Ghost 2.0s: V→↓ Strategy: →↓ then ΛV→→↓

Wave 4 Ghost 0.0s: ֍ Ghost 0.0s: ↓ Ghost 0.9s: Λ Ghost 1.8s: V Ghost 2.7s: → Ghost 3.6s: V↓ Ghost 4.5s: →Λ Ghost 5.4s: ↓V Ghost 6.3s: Λ→ Ghost 7.2s: V↓ Ghost 8.1s: →Λ Ghost 9.0s:: ↓V Ghost 10.0s:: Λ→ Strategy: There's time between each ghost appearance and the next, so take your time, but make sure to kill the last ghost as quickly as possible to set off the next wave.

Boss Stage 1 Ghost 1.8s¤: →→→ Ghost 1.8s¤: ↓↓↓ Boss: →→Λ→→ Strategy: Simple, →→→↓↓↓ then →→Λ→→ for the boss ¤ Timed from boss appearance.

Boss Stage 2 Ghost 1.0s¤¤: →↓→ Ghost 1.0s¤¤: ↓→↓ Ghost 1.0s¤¤: Λ Boss: ↓↓V↓↓ Strategy: →↓→↓Λ then ↓↓V↓↓ for the boss

Boss Stage 3 Ghost 1.0s¤¤: ΛV Ghost 1.0s¤¤: V→ Ghost 1.0s¤¤: →↓ Boss: ↓→Λ→↓ Strategy: ΛV→↓ then ↓→Λ→↓ for the boss ¤ Timed from final boss pattern symbol

Notes: • Strangely enough, failing to kill the ghosts on the second and third stages causes the boss to laugh indefinitely and cause the game to softlock. • It takes 0.6s for the Level 2 boss to transition from ghost to boss pattern. • The time it takes to draw the final symbol to first ghosts appearing in Stage 3 is 18.5s.