:root { --bg: #1a1a1a; --text: #4caf50; }
* { box-sizing: border-box; margin: 0; padding: 0; }
body { font-family: 'Outfit', sans-serif; background: var(--bg); color: var(--text); min-height: 100vh; display: flex;
    flex-direction: column; justify-content: flex-start; align-items: center; }
.game-container { width: 100%; max-width: 500px; padding: 1rem; display: flex; flex-direction: column; align-items: center; position: relative;}
header { width: 100%; display: flex; justify-content: space-between; align-items: center; margin-bottom: 2rem; }
.back-btn { text-decoration: none; background: #00897b; color: white; padding: 10px 20px; border-radius: 20px; font-weight: bold; box-shadow: 0 4px 0 #00695c; }
.back-btn:active { transform: translateY(4px); box-shadow: 0 0 0; }
h1 { font-size: 2rem; color: #009688; text-shadow: 2px 2px 0 #000; }
.hud { font-size: 1.5rem; font-weight: bold; margin-bottom: 2rem; background: rgba(30,30,30,0.95); padding: 10px 20px; border-radius: 20px; }

.question-area { display: flex; align-items: center; justify-content: center; gap: 15px; margin-bottom: 3rem; background: white; padding: 30px; border-radius: 20px; box-shadow: 0 10px 30px rgba(0,0,0,0.1); width: 100%;}
.equation { font-size: 2.5rem; }
.equals { font-size: 3rem; font-weight: bold; color: #ff9800; }
.answer-slot { width: 60px; height: 60px; background: #eee; border-radius: 15px; display: flex; justify-content: center; align-items: center; font-size: 2.5rem; font-weight: bold; color: #fff; border: 3px dashed #ccc;}

.options { display: flex; gap: 20px; }
.option-btn { width: 80px; height: 80px; border-radius: 20px; border: none; background: #4caf50; color: white; font-size: 3rem; font-weight: 900; font-family: 'Outfit'; cursor: pointer; box-shadow: 0 6px 0 #388e3c; transition: transform 0.1s; }
.option-btn:active { transform: translateY(6px); box-shadow: none; }

.feedback { position: absolute; top: 50%; left: 50%; transform: translate(-50%, -50%); font-size: 4rem; font-weight: 900; color: #ffeb3b; text-shadow: 0 0 20px rgba(0,0,0,0.5); z-index: 20; animation: popIn 1s forwards; pointer-events: none;}
@keyframes popIn { 0% { transform: translate(-50%, -50%) scale(0); opacity: 0;} 20% { transform: translate(-50%, -50%) scale(1.2); opacity: 1;} 80% { transform: translate(-50%, -50%) scale(1); opacity: 1;} 100% { transform: translate(-50%, -50%) scale(0); opacity: 0;}}
.hidden { display: none !important; }