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#0003;display:flex;align-items:center;justify-content:center;transform-style:preserve-3d}.flashcard.flipped{transform:rotateY(180deg)}.flashcard-face{position:absolute;width:100%;height:100%;backface-visibility:hidden;display:flex;align-items:center;justify-content:center;top:0;left:0;background:inherit;border-radius:15px}.flashcard-front{z-index:2}.flashcard-back{transform:rotateY(180deg);z-index:1}.word{font-size:2rem;font-weight:700;margin-bottom:15px;text-shadow:2px 2px 4px rgba(0,0,0,.3);text-align:center}.definition{font-size:1rem;line-height:1.5;opacity:.9;text-align:center}.button-group{display:flex;flex-direction:column;gap:10px;margin-top:20px}.btn{padding:12px 20px;border:none;border-radius:10px;font-size:.9rem;font-weight:600;cursor:pointer;transition:all .3s 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#e2e8f0;border-radius:10px;font-size:.9rem;margin-bottom:10px;text-align:center;background:white}.day-input:focus{outline:none;border-color:#4299e1;box-shadow:0 0 0 3px #4299e11a}.day-list-container{max-height:300px;overflow-y:auto;border:2px solid #e2e8f0;border-radius:10px;background:white;margin-bottom:15px}.day-list{display:flex;flex-direction:column}.day-list-item{padding:10px 15px;border:none;background:transparent;text-align:left;cursor:pointer;transition:background-color .2s ease;border-bottom:1px solid #f0f0f0;font-size:.9rem}.day-list-item:hover{background:#f7fafc}.day-list-item.selected{background:#4299e1;color:#fff}.selected-day-info{background:#f7fafc;padding:15px;border-radius:10px;margin-bottom:15px;text-align:center}.selected-day-info p{margin-bottom:5px;font-size:.9rem;color:#4a5568}.celebration{position:fixed;top:0;left:0;width:100%;height:100%;background:rgba(0,0,0,.8);display:flex;align-items:center;justify-content:center;z-index:1000;padding:20px}.celebration-content{background:white;padding:25px;border-radius:15px;text-align:center;max-width:100%;width:100%}.celebration-icon{font-size:3rem;color:#48bb78;margin-bottom:15px}.stats{display:grid;grid-template-columns:repeat(auto-fit,minmax(120px,1fr));gap:15px;margin-top:20px}.stat-card{background:rgba(255,255,255,.9);padding:15px;border-radius:10px;text-align:center;box-shadow:0 4px 12px #0000001a}.stat-number{font-size:1.5rem;font-weight:700;color:#4299e1;margin-bottom:5px}.stat-label{color:#4a5568;font-weight:600;font-size:.8rem}@media (min-width: 768px){.container{max-width:1200px;padding:20px}.header{padding:20px;margin-bottom:30px}.header h1{font-size:2.5rem;margin-bottom:15px}.progress-container{padding:15px;margin-bottom:20px}.progress-bar{height:20px}.progress-text{margin-top:10px;font-size:1rem}.nav-tabs{gap:10px;margin-bottom:20px}.nav-tab{padding:15px 20px;font-size:1rem}.card{padding:40px;max-width:600px}.flashcard{padding:40px;min-height:250px}.word{font-size:2.5rem;margin-bottom:20px}.definition{font-size:1.2rem;line-height:1.6}.button-group{flex-direction:row;gap:15px;margin-top:30px}.btn{width:auto;min-width:120px;padding:15px 30px;font-size:1rem}.day-selector{padding:40px;max-width:500px}.day-selector h2{font-size:2rem;margin-bottom:30px}.day-input{padding:15px;font-size:1rem;margin-bottom:20px}.day-list-container{max-height:400px}.day-list-item{padding:12px 20px;font-size:1rem}.selected-day-info{padding:20px;margin-bottom:20px}.selected-day-info p{font-size:1rem}.celebration-content{padding:40px;max-width:400px}.celebration-icon{font-size:4rem;margin-bottom:20px}.stats{grid-template-columns:repeat(auto-fit,minmax(200px,1fr));gap:20px;margin-top:30px}.stat-card{padding:20px}.stat-number{font-size:2rem}.stat-label{font-size:1rem}}.card{margin-bottom:20px}