diff --git a/src/stage/objects/crystal.css b/src/stage/objects/crystal.css
index 64f0a1a..67f9b58 100644
--- a/src/stage/objects/crystal.css
+++ b/src/stage/objects/crystal.css
@@ -6,3 +6,11 @@
     transform: rotate(calc(90deg + 360deg * var(--rotation-factor)));
   }
 }
+
+.crystal--energy-indicator {
+  stroke-opacity: 1;
+}
+
+.crystal--powerless .crystal--energy-indicator {
+  stroke-opacity: 0;
+}
\ No newline at end of file
diff --git a/src/stage/objects/crystal.tsx b/src/stage/objects/crystal.tsx
index 3379d99..3810ff0 100644
--- a/src/stage/objects/crystal.tsx
+++ b/src/stage/objects/crystal.tsx
@@ -1,6 +1,8 @@
 import { styled } from "solid-styled-components";
 import { vector2d } from "../vector";
-import { createMemo, createSignal, onCleanup, onMount } from "solid-js";
+import { createMemo, createSignal } from "solid-js";
+import { useTimer } from "../providers/timer";
+import { checkElementOverlap } from "./collision";
 
 import "./crystal.css";
 
@@ -23,14 +25,35 @@ export default function Crystal(props: { size?: number; position?: vector2d }) {
 
   const rechargeProgress = createMemo(() => (energy() / maxEnergy()) * 100);
 
-  function updateEnergy() {
-    setEnergy(energy() - 1);
+  const isAlive = createMemo(() => energy() > 0);
+
+  function checkAnyPlayerUnderCrystal() {
+    const players = document.querySelectorAll<HTMLElement>(".player");
+    const crystal = document.querySelector<HTMLElement>(".crystal");
+
+    for (const player of players) {
+      if (crystal && checkElementOverlap(crystal, player)) {
+        return true;
+      }
+    }
+    return false;
   }
 
-  onMount(() => {
-    const loop = setInterval(() => updateEnergy(), 100);
-    onCleanup(() => clearInterval(loop));
-  });
+  function updateEnergy() {
+    const doRecharge = checkAnyPlayerUnderCrystal();
+    if (doRecharge) {
+      if (energy() < maxEnergy()) {
+        setEnergy(energy() + 1);
+      }
+    } else {
+      if (energy() > 0) {
+        setEnergy(energy() - 1);
+      }
+    }
+  }
+
+  const [{ subscribe }] = useTimer();
+  subscribe(() => updateEnergy());
 
   // Renderer
 
@@ -61,9 +84,10 @@ export default function Crystal(props: { size?: number; position?: vector2d }) {
     stroke-linecap: round;
 
     animation: alternate 10s crystal--fill-wabble infinite ease-in-out;
+
     transform-origin: var(--half-size) var(--half-size);
     stroke-dasharray: var(--dash) calc(var(--circumference) - var(--dash));
-    transition: stroke-dasharray 0.3s linear 0s;
+    transition: all 0.3s linear 0s;
     stroke: var(--color-primary);
   `;
 
@@ -80,7 +104,7 @@ export default function Crystal(props: { size?: number; position?: vector2d }) {
 
   return (
     <CrystalElement
-      class="crystal"
+      class={`crystal ${isAlive() ? `crystal--powerful` : `crystal--powerless`}`}
       style={{
         left: `${x()}px`,
         top: `${y()}px`,
@@ -91,7 +115,7 @@ export default function Crystal(props: { size?: number; position?: vector2d }) {
       }}
     >
       <CrystalCircleInactive />
-      <CrystalCircleActive />
+      <CrystalCircleActive class="crystal--energy-indicator" />
     </CrystalElement>
   );
 }