data/items.js

@@ -1504,13 +1504,8 @@ let BattleItems = {
 		fling: {
 			basePower: 10,
 		},
-		onStart(pokemon) {
-			if (!pokemon.ignoringItem() && this.isTerrain('electricterrain') && pokemon.useItem()) {
-				this.boost({def: 1});
-			}
-		},
-		onAnyTerrainStart() {
-			if (this.isTerrain('electricterrain') && this.effectData.target.useItem()) {
+		onUpdate(pokemon) {
+			if (this.isTerrain('electricterrain') && pokemon.useItem()) {
 				this.boost({def: 1});
 			}
 		},
@@ -2170,13 +2165,8 @@ let BattleItems = {
 		fling: {
 			basePower: 10,
 		},
-		onStart(pokemon) {
-			if (!pokemon.ignoringItem() && this.isTerrain('grassyterrain') && pokemon.useItem()) {
-				this.boost({def: 1});
-			}
-		},
-		onAnyTerrainStart() {
-			if (this.isTerrain('grassyterrain') && this.effectData.target.useItem()) {
+		onUpdate(pokemon) {
+			if (this.isTerrain('grassyterrain') && pokemon.useItem()) {
 				this.boost({def: 1});
 			}
 		},
@@ -3619,13 +3609,8 @@ let BattleItems = {
 		fling: {
 			basePower: 10,
 		},
-		onStart(pokemon) {
-			if (!pokemon.ignoringItem() && this.isTerrain('mistyterrain') && pokemon.useItem()) {
-				this.boost({spd: 1});
-			}
-		},
-		onAnyTerrainStart() {
-			if (this.isTerrain('mistyterrain') && this.effectData.target.useItem()) {
+		onUpdate(pokemon) {
+			if (this.isTerrain('mistyterrain') && pokemon.useItem()) {
 				this.boost({spd: 1});
 			}
 		},
@@ -4426,13 +4411,8 @@ let BattleItems = {
 		fling: {
 			basePower: 10,
 		},
-		onStart(pokemon) {
-			if (!pokemon.ignoringItem() && this.isTerrain('psychicterrain') && pokemon.useItem()) {
-				this.boost({spd: 1});
-			}
-		},
-		onAnyTerrainStart() {
-			if (this.isTerrain('psychicterrain') && this.effectData.target.useItem()) {
+		onUpdate(pokemon) {
+			if (this.isTerrain('psychicterrain') && pokemon.useItem()) {
 				this.boost({spd: 1});
 			}
 		},

data/mods/ssb/scripts.js

@@ -287,7 +287,6 @@ let BattleScripts = {
 		}
 		// Always run a terrain end event to prevent a visual glitch with custom terrains
 		if (prevTerrain) this.singleEvent('End', this.getEffect(prevTerrain), prevTerrainData, this);
-		this.runEvent('TerrainStart', source, source, status);
 		return true;
 	},
 	pokemon: {

dev-tools/globals.ts

@@ -186,7 +186,6 @@ interface EventMethods {
 	onAnyDamage?: (this: Battle, damage: number, target: Pokemon, source: Pokemon, effect: Effect) => void
 	onAnyBasePower?: (this: Battle, basePower: number, source: Pokemon, target: Pokemon, move: ActiveMove) => void
 	onAnySetWeather?: (this: Battle, target: Pokemon, source: Pokemon, weather: PureEffect) => void
-	onAnyTerrainStart?: (this: Battle) => void
 	onAnyModifyDamage?: (this: Battle, damage: number, source: Pokemon, target: Pokemon, move: ActiveMove) => void
 	onAnyRedirectTarget?: (this: Battle, target: Pokemon, source: Pokemon, source2: Pokemon, move: ActiveMove) => void
 	onAnyAccuracy?: (this: Battle, accuracy: number, target: Pokemon, source: Pokemon, move: ActiveMove) => void

sim/battle.js

@@ -321,7 +321,6 @@ class Battle extends Dex.ModdedDex {
 			this.terrainData = prevTerrainData;
 			return false;
 		}
-		this.runEvent('TerrainStart', source, source, status);
 		return true;
 	}
 

test/simulator/items/seeds.js

@@ -11,24 +11,14 @@ describe('Seeds', function () {
 	});
 
 	it('should activate even in a double-switch-in', function () {
-		battle = common.createBattle([
-			[{species: 'Tapu Koko', ability: 'electricsurge', item: 'grassyseed', moves: ['protect']}],
-			[{species: 'Tapu Bulu', ability: 'grassysurge', item: 'electricseed', moves: ['protect']}],
+		battle = common.createBattle();
+		const p1 = battle.join('p1', 'Guest 1', 1, [
+			{species: 'tapukoko', ability: 'electricsurge', item: 'grassyseed', moves: ['protect']},
 		]);
-		assert.false(battle.p1.active[0].item);
-		assert.false(battle.p2.active[0].item);
-	});
-
-	it('should not activate when Magic Room ends', function () {
-		battle = common.createBattle([
-			[
-				{species: 'Tapu Koko', ability: 'electricsurge', item: 'terrainextender', moves: ['protect']},
-				{species: 'Hawlucha', ability: 'unburden', item: 'electricseed', moves: ['protect']},
-			],
-			[{species: 'Alakazam', ability: 'magicguard', moves: ['magicroom']}],
+		const p2 = battle.join('p2', 'Guest 2', 1, [
+			{species: 'tapubulu', ability: 'grassysurge', item: 'electricseed', moves: ['protect']},
 		]);
-		battle.makeChoices('move protect', 'move magicroom');
-		battle.makeChoices('switch 2', 'move magicroom');
-		assert.strictEqual(battle.p1.active[0].item, 'electricseed');
+		assert.false(p1.active[0].item);
+		assert.false(p2.active[0].item);
 	});
 });