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Trap

Trap: Trap and 18 more

Sets a trap that captures the enemy that steps in.

19 spells the game runs with the same code.

CapturesSummons or places
The same in all of them:Intended chance at 0 HP: 99.2 %Trigger radius: 16 pxPower: 128Aim: Tap a pointAffects: Enemies
How is the total effect worked out?

All 19 work the same way. A regular wild monster at or under the HP limit (the exact value counts: with 128 max HP, Trap catches 32 and not 33) is always caught; the caster’s magic, the drawing and the rank do not raise the limit. The trap checks units in the order of the game’s list, not the nearest or the weakest: if the first eligible one has too much HP, the trap is spent on it. Fire Trap and Water Trap differ only in element: their power 128 is a same-element factor of 1, not damage, and they freeze or burn nothing. Obey and Order skip units of the opposite element without spending the trap. All else equal, the cheapest trap whose limit covers the target’s HP is the better choice; a higher tier pays off for more HP, a longer reach (40, 65, 110 and 160 px) or a longer time (4 to 6 s).

Total effect: what one unit receives over the whole spell. The real figure depends on who casts and who receives it, so it is worked out for a fixed reference: the caster has magic 30 (Isaac at level 1), the element at level 1–10 and a perfect stroke (quality 1); the receiver has defense and magic defense 0, a neutral element and no weakness or shield; no random factor. “up to” is a maximum that needs every hit to land, or the unit to stay where the spell reaches it; “not confirmed” marks what the code read so far does not settle.

To cast a spell you draw its runes, each in one stroke and each scored on its own: a long stroke with many turns takes longer and gives more chances to slip out of the shape. Each spell shows its runes, drawn from their strokes, with their level (I to III) and how long their strokes are added up, in widths of the rune: the game scales the drawing, so its size on screen does not count. A higher level is usually longer, but not always (Water II is shorter than Wind I).

Best spells · Which spells pay off and why, each with the number behind it. The filters leave only what Isaac already has at hand.

Trap

30 MP

Range
65 px
Lasts
4 s

Fire

Wind

Water

Earth

Dark

Light

Obey

50 MP

Range
110 px
Lasts
5 s

Fire

Wind

Water

Earth

Dark

Light

Order

65 MP

Range
160 px
Lasts
6 s

Fire

Wind

Water

Earth

Dark

Light

Others

Dark

Worked out for a caster with magic 30 and a perfect stroke, against defense and magic defense 0, with no random factor. How is it worked out?

Grouped by the effect class and subkind of each spell in the game’s data, as the research did; the notes come from reading the code, not from playing.

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