:root {
    --primary-pink: #ff69b4;
    --secondary-pink: #ff1493;
    --light-pink: #ffb6c1;
    --white: #ffffff;
    --glass-bg: rgba(255, 255, 255, 0.15);
    --shadow: 0 25px 45px rgba(0, 0, 0, 0.1);
}

        * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }

        body {
            /* Use Poppins (loaded with latin-ext) for Vietnamese support; fall back to system fonts */
            font-family: 'Poppins', 'Quicksand', 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
            min-height: 100vh;
            display: flex;
            justify-content: center;
            align-items: center;
            overflow-x: hidden;
            background: linear-gradient(-45deg, #f5c1d7, #e7acc9, #f5b5d0, #f8cee3);
            background-size: 400% 400%;
            animation: bgmove 10s ease-in-out infinite;
        }
        @keyframes bgmove {
            0% {background-position: 0% 50%;}
            50% {background-position: 100% 50%;}
            100% {background-position: 0% 50%;}
        }
        .animated-bg {
            display: none !important;
        }

        /* Hiệu ứng chuyển động nhẹ nhàng */
        @keyframes subtleFloat {
            0%   { transform: scale(1) translateY(0px) translateX(0px);}
            25%  { transform: scale(1.03) translateY(-10px) translateX(10px);}
            50%  { transform: scale(1.01) translateY(10px) translateX(-10px);}
            75%  { transform: scale(1.04) translateY(-5px) translateX(5px);}
            100% { transform: scale(1) translateY(0px) translateX(0px);}
        }

        /* Optimized sparkle effects */
        .sparkle {
            position: absolute;
            background: radial-gradient(circle, rgba(255, 255, 255, 0.9) 0%, transparent 70%);
            border-radius: 50%;
            animation: sparkleFloat linear infinite;
            z-index: -2;
            will-change: transform, opacity;
        }

        @keyframes sparkleFloat {
            0% {
                transform: translateY(100vh) rotate(0deg) scale(0);
                opacity: 0;
            }
            10% { opacity: 1; }
            90% { opacity: 1; }
            100% {
                transform: translateY(-50px) rotate(360deg) scale(1);
                opacity: 0;
            }
        }

        /* Enhanced flower animation */
        .flower {
            position: absolute;
            font-size: 25px;
            animation: flowerFall linear infinite;
            z-index: -1;
            text-shadow: 0 0 15px rgba(255, 182, 193, 0.8);
            will-change: transform, opacity;
        }

        @keyframes flowerFall {
            0% {
                transform: translateY(-50px) rotateX(0deg) rotateY(0deg) rotateZ(0deg);
                opacity: 1;
            }
            50% {
                transform: translateY(50vh) rotateX(180deg) rotateY(180deg) rotateZ(180deg);
                opacity: 0.8;
            }
            100% {
                transform: translateY(110vh) rotateX(360deg) rotateY(360deg) rotateZ(360deg);
                opacity: 0;
            }
        }

        /* Main container */
        .container {
            display: flex;
            flex-direction: column;
            justify-content: center;
            align-items: center;
            padding: 24px 0;
            position: relative;
            z-index: 1;
            background: rgba(255,255,255,0.13);
            box-shadow: 0 8px 32px 0 rgba(255, 182, 213, 0.18), 0 1.5px 8px 0 rgba(255, 182, 213, 0.10);
            border-radius: 32px;
            max-width: 500px;
            width: 100%;
            max-width: auto;
            height: auto;
            margin: 40px auto;
            transition: 
                box-shadow 0.4s cubic-bezier(0.175, 0.885, 0.32, 1.275),
                transform 0.4s cubic-bezier(0.175, 0.885, 0.32, 1.275),
                border-color 0.4s,
                background 0.4s;
        }

        /* Calculator screen và Birthday screen nền hồng mờ, viền hồng nhạt */
        .calculator-screen,
        .birthday-screen {
    background: none !important;
    box-shadow: none !important;
    border: none !important;
    backdrop-filter: none !important;
    padding: 0 !important;
    max-width: none !important;
    width: auto !important;
    border-radius: 0 !important;
}
        

        /* Khi hover nổi bật hơn một chút */
        .container:hover,
        .birthday-screen:hover {
            box-shadow: 0 20px 45px rgba(252, 189, 198, 0.25);
            border-color: #eb9ec6;
            transform: scale(1.02);
        }

        .calculator-title {
            background: linear-gradient(135deg, #cc7986 0%, #fd537d 60%, #f0749d 100%);
            -webkit-background-clip: text;
            -webkit-text-fill-color: transparent;
            background-clip: text;
            font-size: 28px;
            font-weight: 800;
            margin-bottom: 25px;
            text-shadow: 0 2px 4px rgba(247, 152, 199, 0.3);
        }

        @keyframes titleGlow {
            0% { filter: brightness(1) contrast(1); }
            100% { filter: brightness(1.3) contrast(1.1); }
        }

        @keyframes gradientMove {
            0% { background-position: 0% 50%; }
            50% { background-position: 100% 50%; }
            100% { background-position: 0% 50%; }
        }

        /* Enhanced display */
        .display {
            width: 90%;
            height: 55px;
            background: linear-gradient(135deg, #ffd1dc, #ffb6d5, #f1c9dd, #ffd1dc);
            background-size: 400% 400%;
            animation: bgmove 10s ease-in-out infinite;
            border: 2.5px solid rgba(255, 182, 213, 0.35); /* hồng nhạt, mờ */
            border-radius: 20px;
            font-size: 28px;
            text-align: right;
            padding: 0 25px;
            margin-bottom: 30px;
            outline: none;
            letter-spacing: 4px;
            font-weight: bold;
            color: #c2185b;
            text-shadow: 0 2px 8px #fff8;
            box-shadow: inset 0 6px 12px rgba(0, 0, 0, 0.1),
                0 4px 8px rgba(255, 105, 180, 0.1);
            transition: all 0.3s ease;
            backdrop-filter: blur(5px);
        }

        .display:focus {
            border-color: var(--primary-pink);
            box-shadow: 
                inset 0 6px 12px rgba(0, 0, 0, 0.1),
                0 0 25px rgba(255, 105, 180, 0.4),
                0 0 50px rgba(255, 105, 180, 0.2);
            transform: scale(1.02);
        }

        /* Bàn phím: bo góc lớn, hiệu ứng bóng hồng nhẹ, nền mờ trong suốt */
        .buttons {
            display: grid;
            grid-template-columns: repeat(3, 1fr);
            gap: 18px;
            margin: 18px auto 0 auto;
            width: 100%;
            max-width: 100%;
            background-size: 400% 400%;
            animation: bgmove 10s ease-in-out infinite;
            border-radius: 28px;
            box-shadow: 0 6px 32px 0 #ffb6c155, 0 2px 8px #f18dbf55;
            /* Xóa border */
            border: none;
            padding: 22px 0 18px 0;
            transition: box-shadow 0.3s, border-color 0.3s;
        }

        /* Enhanced button styles */
        .btn {
            height: 70px;
    width: 100%;
    border: none;
    border-radius: 22px;
    font-size: 28px;
    font-weight: bold;
    cursor: pointer;
    transition: all 0.18s cubic-bezier(0.175, 0.885, 0.32, 1.275);
    position: relative;
    overflow: hidden;
    backdrop-filter: blur(10px);
    margin: 0;
    padding: 0;
    min-width: 0;
    box-sizing: border-box;
    background: linear-gradient(135deg, #ffb6d5, #fdb1d7, #ffd1dc, #ffb6d5);
    background-size: 400% 400%;
    animation: bgmove 10s ease-in-out infinite;
    color: #fff;
    font-weight: 700;
    box-shadow: 0 2px 8px #ffb6c133;
        }

        .btn::before {
            content: '';
            position: absolute;
            top: 0;
            left: -100%;
            width: 100%;
            height: 100%;
            background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.4), transparent);
            transition: left 0.6s ease;
        }

        .btn:hover::before {
            left: 100%;
        }

        .btn:hover {
            transform: translateY(-8px) scale(1.05);
            box-shadow: 0 20px 40px rgba(0, 0, 0, 0.2);
        }

        .btn:active {
            transform: translateY(-3px) scale(0.98);
            transition: all 0.1s ease;
        }

        .btn-number {
            background: linear-gradient(135deg, #f19bc0 0%, #f7a8ce 60%, #f09dc9 100%);
            color: #fff;
            border: none;
            font-weight: 700;
            font-size: 1.15rem;
            border-radius: 14px;
            transition: all 0.18s;
            height: 38px;
            min-width: 0;
            box-shadow: 0 2px 8px #ffb6c133;
        }
        .btn-number:hover, .btn-number:focus {
            background: linear-gradient(135deg, #f1a6cc 0%, #e696c0 100%);
            color: #fff;
            box-shadow: 0 0 12px #eb97c1bb;
        }

        .btn-clear, .btn-enter {
            background: linear-gradient(135deg, #ffd1dc, #ffb6c1);
            color: #eea2cb;
            border: none;
            font-weight: 700;
            font-size: 1.15rem;
            border-radius: 14px;
            height: 38px;
            min-width: 0;
            box-shadow: 0 2px 8px #ffb6c133;
            transition: all 0.18s;
        }
        .btn-clear:hover, .btn-enter:hover,
        .btn-clear:focus, .btn-enter:focus {
            background: linear-gradient(135deg, #f1bcc4, #ffd1dc);
            color: #f8b2d5;
            box-shadow: 0 0 12px #ffd1dcaa;
        }

        /* Ẩn các nút + - . */
        .btn-number:nth-child(13),
        .btn-number:nth-child(15),
        .btn-number:nth-child(16) {
            display: none !important;
        }
        

        /* Enhanced birthday screen */

.birthday-screen,
.birthday-screen .letter-container,
.birthday-screen .letter-opened,
.birthday-screen .letter-closed {
    background: none !important;
    box-shadow: none !important;
    border: none !important;
    border-radius: 0 !important;
    padding: 0 !important;
}
        @keyframes birthdayEntrance {
            0% {
                opacity: 0;
                transform: scale(0.3) rotate(-15deg);
            }
            50% {
                transform: scale(1.1) rotate(5deg);
            }
            100% {
                opacity: 1;
                transform: scale(1) rotate(0deg);
            }
        }

        .birthday-title {
            background: linear-gradient(45deg, 
                var(--secondary-pink), var(--primary-pink), 
                #ffd700, #ff4081, var(--secondary-pink));
            background-size: 300% 300%;
            -webkit-background-clip: text;
            -webkit-text-fill-color: transparent;
            background-clip: text;
            font-size: 48px;
            font-weight: 900;
            margin-bottom: 30px;
            animation: rainbowText 4s ease-in-out infinite, 
            titleBounce 2s ease-in-out infinite;
        }

        @keyframes rainbowText {
            0%, 100% { background-position: 0% 50%; }
            50% { background-position: 100% 50%; }
        }

        @keyframes titleBounce {
            0%, 100% { transform: translateY(0); }
            50% { transform: translateY(-10px); }
        }

        .cake {
            font-size: 120px;
            margin: 30px 0;
            animation: cakeParty 2.5s ease-in-out infinite;
            filter: drop-shadow(0 0 30px rgba(255, 215, 0, 0.7));
        }

        @keyframes cakeParty {
            0%, 100% {
                transform: rotate(0deg) scale(1);
            }
            25% {
                transform: rotate(-15deg) scale(1.1);
            }
            75% {
                transform: rotate(15deg) scale(1.1);
            }
        }

        .date-special {
            background: linear-gradient(45deg, #e2aac6, #f080af, #ec728e, #ff69b4);
            background-size: 300% 300%;
            -webkit-background-clip: text;
            -webkit-text-fill-color: transparent;
            background-clip: text;
            font-size: 36px;
            font-weight: bold;
            margin: 30px 0;
            text-shadow: 0 4px 16px #f3c2c2, 0 2px 8px #df94b3;
            animation: rainbowText 4s ease-in-out infinite;
        }

        .birthday-message {
            color: #444;
            font-size: 22px;
            margin: 30px 0;
            line-height: 1.8;
            font-weight: 500;
            text-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
            animation: messageFloat 3s ease-in-out infinite;
        }

        @keyframes messageFloat {
            0%, 100% { transform: translateY(0); }
            50% { transform: translateY(-5px); }
        }

        .back-btn {
            background: linear-gradient(135deg, var(--primary-pink), var(--secondary-pink));
            color: white;
            border: none;
            padding: 18px 45px;
            border-radius: 35px;
            font-size: 20px;
            font-weight: bold;
            cursor: pointer;
            margin-top: 30px;
            transition: all 0.4s cubic-bezier(0.175, 0.885, 0.32, 1.275);
            box-shadow: 0 15px 30px rgba(255, 105, 180, 0.4);
            position: relative;
            overflow: hidden;
            border: 2px solid rgba(255, 255, 255, 0.3);
            background: linear-gradient(135deg, #ffb6d5, #ff69b4, #ffd1dc, #ffb6d5);
            background-size: 400% 400%;
            animation: bgmove 10s ease-in-out infinite;
            color: #fff;
            font-weight: 700;
            font-size: 1.15rem;
            box-shadow: 0 2px 8px #ffb6c133;
        }

        .back-btn::before {
            content: '';
            position: absolute;
            top: 0;
            left: -100%;
            width: 100%;
            height: 100%;
            background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.4), transparent);
            transition: left 0.6s ease;
        }

        .back-btn:hover::before {
            left: 100%;
        }

        .back-btn:hover {
            transform: translateY(-5px) scale(1.05);
            box-shadow: 0 20px 40px rgba(240, 186, 213, 0.5);
        }

    /* Thiệp sinh nhật 3D - font imports moved to HTML head for better control */

        .birthday-card-section {
            margin: 0 0 40px 0;
            z-index: 10;
            position: relative;
            display: flex;
            justify-content: center;
            align-items: center;
        }

        .card-3d {
            /* Prefer handwriting fonts loaded in head; include Vietnamese-capable fallbacks */
            font-family: 'Dancing Script', 'Indie Flower', 'Amatic SC', 'Poppins', cursive, 'Segoe UI', Roboto, Arial, sans-serif !important;
            color: #013243;
            position: relative;
            width: 320px;
            height: 420px;
            background: linear-gradient(135deg, #ffd1dc, #ffb6d5);
            transform-style: preserve-3d;
            transform: perspective(2000px);
            /* Sửa lại box-shadow cho đẹp hơn */
            box-shadow: 
                0 20px 40px rgba(255, 105, 180, 0.3),
                0 10px 20px rgba(255, 182, 213, 0.2),
                inset 0 1px 0 rgba(255, 255, 255, 0.3);
            transition: 1.2s cubic-bezier(0.175, 0.885, 0.32, 1.275);
            border-radius: 15px;
            cursor: pointer;
            /* Thêm viền đẹp */
            border: 2px solid rgba(255, 255, 255, 0.4);
        }

        .card-3d:hover {
            transform: perspective(2000px) rotateY(15deg) scale(1.1);
            /* Sửa lại hover shadow */
            box-shadow: 
                0 30px 60px rgba(255, 105, 180, 0.4),
                0 15px 30px rgba(255, 182, 213, 0.3),
                inset 0 1px 0 rgba(255, 255, 255, 0.5);
        }

        /* Xóa hoặc sửa lại các pseudo-element */
        .card-3d:before {
            content: '';
            position: absolute;
            top: -3px;
            left: -3px;
            right: -3px;
            bottom: -3px;
            background: linear-gradient(45deg, #ff69b4, #ffb6d5, #ffd1dc, #ff69b4);
            background-size: 400% 400%;
            animation: borderGlow 3s ease infinite;
            border-radius: 18px;
            z-index: -1;
        }

        @keyframes borderGlow {
            0%, 100% { background-position: 0% 50%; }
            50% { background-position: 100% 50%; }
        }

        .card-3d:after {
            content: '';
            position: absolute;
            top: 0;
            left: 0;
            right: 0;
            bottom: 0;
            background: linear-gradient(135deg, rgba(255, 255, 255, 0.1), rgba(255, 255, 255, 0.05));
            border-radius: 15px;
            pointer-events: none;
        }

        .card-imgBox {
            width: 100%;
            height: 100%;
            position: relative;
            transform-origin: left;
            transition: 1s ease;
            border-radius: 15px;
            overflow: hidden;
        }

        .card-bark {
            position: absolute;
            background: linear-gradient(135deg, #ffd1dc, #ffb6d5);
            width: 100%;
            height: 100%;
            opacity: 0;
            transition: 1s ease;
            border-radius: 15px;
        }

        .card-imgBox img {
            width: 100%;
            height: 100%;
            object-fit: cover;
            border-radius: 15px;
        }

        .card-3d:hover .card-imgBox {
            transform: rotateY(-135deg);
        }

        .card-3d:hover .card-bark {
            opacity: 1;
            transition: 0.8s;
            box-shadow: 300px 200px 100px rgba(255, 105, 180, 0.3) inset;
        }

        /* SỬA LẠI - Chữ trong thiệp hiển thị tĩnh, không chạy */
        .card-details {
            position: absolute;
            top: 50%; /* Căn giữa theo chiều dọc */
            left: 50%; /* Căn giữa theo chiều ngang */
            width: 100%;
            height: auto;
            transform: translate(-50%, -50%); /* Dịch chuyển về giữa hoàn toàn */
            box-sizing: border-box;
            padding: 20px;
            z-index: -1;
            display: flex;
            flex-direction: column;
            justify-content: center;
            align-items: center;
            text-align: center;
        }

        .card-details h4 {
            font-size: 23px;
            line-height: 1.1;
            color: #C0392B;
            text-align: center;
            margin-bottom: 20px;
            font-weight: bold;
            margin-top: 0;
        }

        .card-details p {
            font-size: 16px;
            line-height: 1.3;
            padding: 1px 0;
            color: #013243;
            font-weight: 400;      /* Định dạng thường */
            font-style: normal;    /* Sửa lại: không nghiêng */
            margin: 3px 0;
            opacity: 1;
            text-align: left;
        }

        /* Responsive cho thiệp 3D */
        @media (max-width: 480px) {
            .card-3d {
                width: 270px;
                height: auto;
                min-height: 360px;
            }
            .card-details h4 {
                font-size: 21px;
                font-family: 'Poppins', Arial, sans-serif !important;
            }

        }
    
    .card-details p {
        font-size: 13px;
    }

        /* Responsive design */
        @media (max-width: 480px) {
            .calculator-screen, .birthday-screen {
                padding: 25px;
                margin: 10px;
                border-radius: 25px;
            }
            
            .calculator-title {
                font-size: 26px;
                font-family: 'Dancing Script', 'Indie Flower', 'Amatic SC', 'Poppins', cursive, 'Segoe UI', Roboto, Arial, sans-serif !important;

            }
            
            .birthday-title {
                font-size: 32px;
            }
            
            .display {
                height: 65px;
                font-size: 24px;
                padding: 0 20px;
            }
            
            .btn {
                height: 60px;
                font-size: 20px;
            }
            
            .cake {
                font-size: 80px;
            }
            
            .birthday-message {
                font-size: 18px;
            }
        }

        @media (max-width: 1366px) {
            body {
                padding: 10px;
                font-size: 1rem;
            }
            .container {
                max-width: 90%;
                margin: 20px auto;
            }
            .calculator-screen {
                padding: 15px;
                border-radius: 20px;
            }
            .buttons {
                gap: 12px;
            }
            .btn {
                height: 60px;
                font-size: 1.2rem;
            }
            .display {
                font-size: 1.5rem;
                padding: 10px;
            }
        }

        /* Performance optimizations */
        .sparkle, .flower {
            transform: translateZ(0);
            backface-visibility: hidden;
        }

        /* Preload animations */
        .preload * {
            animation-duration: 0s !important;
            animation-delay: 0s !important;
            transition-duration: 0s !important;
        }

        .colorful-gradient {
            position: fixed;
            top: 0; left: 0; width: 100vw; height: 100vh;
            pointer-events: none;
            z-index: -2;
            background: linear-gradient(120deg, #ffb6c1 0%, #ff69b4 30%, #ffd700 60%, #a18cd1 100%);
            opacity: 0.55;
            mix-blend-mode: lighten;
            animation: gradientMove 12s ease-in-out infinite alternate;
        }
        @keyframes gradientMove {
            0% { background-position: 0% 50%; }
            100% { background-position: 100% 50%; }
        }
        /* Responsive cho thiệp 3D */
@media (max-width: 768px) {
    .card-3d {
        width: 280px;
        height: 380px;
    }
    
    .card-details {
        padding: 15px;
    }
    
    .card-details h4 {
        font-size: 22px;
        margin-bottom: 15px;
    }
    
    .card-details p {
        font-size: 13px;
        margin: 2px 0;
        line-height: 1.2;
    }
}

@media (max-width: 480px) {
    .card-3d {
        width: 250px;
        height: 340px;
    }
    
    .card-details {
        padding: 12px;
    }
    
    .card-details h4 {
        font-size: 20px;
        margin-bottom: 12px;
    }
    
    .card-details p {
        font-size: 12px;
        margin: 1px 0;
    }
}

        /* Confetti styles */
        .confetti {
            position: fixed;
            top: 50%;
            left: 50%;
            width: 10px;
            height: 10px;
            background: hsl(0, 90%, 60%);
            opacity: 0.9;
            pointer-events: none;
            animation: confettiFall 2s ease-out forwards;
        }

        @keyframes confettiFall {
            0% {
                transform: translate(-50%, -50%) scale(1);
                opacity: 1;
            }
            100% {
                transform: translate(-50%, 100vh) scale(0.5);
                opacity: 0;
            }
        }

        .calculator-title-with-avatar {
            display: flex;
            align-items: center;
            justify-content: center;
            gap: 18px;
            margin-bottom: 18px;
        }

        .avatar-upload {
            cursor: pointer;
            display: flex;
            align-items: center;
        }

        .avatar-circle {
            width: 48px;
            height: 48px;
            border-radius: 50%;
            background: linear-gradient(135deg, #ffb6d5 60%, #ffd1dc 100%);
            border: 2px solid #fff0f6;
            display: flex;
            align-items: center;
            justify-content: center;
            overflow: hidden;
            position: relative;
            box-shadow: 0 2px 8px #ffb6c133;
            transition: box-shadow 0.2s;
        }

        .avatar-circle:hover {
            box-shadow: 0 4px 16px #ffb6d155;
        }

        .avatar-circle img {
            width: 100%;
            height: 100%;
            object-fit: cover;
            display: block;
        }

        #avatarPlaceholder {
            font-size: 2em;
            color: #ff69b4;
            font-weight: bold;
            user-select: none;
        }

        .avatar-square {
            width: 150px;
            height: 150px;
            border-radius: 12px;
            background: linear-gradient(135deg, #ffb6d5 60%, #ffd1dc 100%);
            border: 2.5px solid rgba(255, 182, 213, 0.35);
            display: flex;
            align-items: center;
            justify-content: center;
            overflow: hidden;
            position: relative;
            box-shadow: 0 8px 32px 0 rgba(255, 182, 213, 0.18), 0 1.5px 8px 0 rgba(255, 182, 213, 0.10);
            transition: box-shadow 0.2s;
        }

        .avatar-square:hover {
            box-shadow: 0 4px 16px #ffb6d155;
        }

        .avatar-square img {
            width: 100%;
            height: 100%;
            object-fit: cover;
            display: block;
        }

        @keyframes keyEffect {
            0% {
                transform: scale(1) rotate(0deg);
                opacity: 1;
            }
            50% {
                transform: scale(1.05) rotate(5deg);
                opacity: 0.8;
            }
            100% {
                transform: scale(1) rotate(0deg);
                opacity: 1;
            }
        }

        .input-avatar-row {
    display: flex;
    align-items: flex-start;
    justify-content: center;
    gap: 32px;
    width: 100%;
}

.avatar-square {
    flex-shrink: 0;
}

.input-and-keypad {
    flex: 1;
    display: flex;
    flex-direction: column;
    align-items: flex-end;
    width: 100%;
    max-width: 260px;
}

.input-and-keypad .calculator-title {
    align-self: flex-end;
    margin-bottom: 18px;
}

.input-and-keypad .display {
    align-self: flex-end;
    margin-bottom: 18px;
}

.input-and-keypad .buttons {
    align-self: flex-end;
}

.letter-container {
    display: flex;
    flex-direction: column;
    align-items: center;
    margin: 30px 0;
    min-height: unset;
    justify-content: center;
}

.letter-closed {
    cursor: pointer;
    display: flex;
    flex-direction: column;
    align-items: center;
    transition: transform 0.2s;
    user-select: none;
}
.letter-closed:hover {
    transform: scale(1.07) rotate(-3deg);
}

.letter-text {
    margin-top: 12px;
    font-size: 1.2em;
    color: #ff69b4;
    font-weight: bold;
    text-shadow: 0 2px 8px #fff;
}

.letter-opened {
    flex-direction: column;
    align-items: center;
    width: 100%;
    display: flex;
    justify-content: flex-start;
    text-align: center;
    min-height: 350px;
    position: relative;
}

@keyframes letterOpenAnim {
    0% { transform: scale(0.7) rotate(-10deg); opacity: 0; }
    80% { transform: scale(1.1) rotate(3deg); opacity: 1; }
    100% { transform: scale(1) rotate(0deg); opacity: 1; }
}
.heart-gallery {
    position: fixed;
    top: 50%;
    left: 50%;
    width: 1100px;
    height: 110px;
    margin: 0;
    display: flex;
    justify-content: center;
    align-items: center;
    pointer-events: none;
    transform: translate(-50%, -50%);
    z-index: 1100;
}
#openGiftBtn {
    display: none;
    margin: 30px auto 0 auto;
    text-align: center;
}
.heart-gallery .heart-img {
    position: absolute;
    width: 170px;    /* tăng kích thước ảnh */
    height: 170px;
    border-radius: 36px;
    object-fit: cover;
    box-shadow: 0 4px 18px #ffb6d1bb, 0 1.5px 8px #ffb6d1aa;
    opacity: 0;
    transform: scale(0.5);
    transition: opacity 0.6s, transform 0.6s;
    border: 3px solid #fff0f6;
    background: #fff;
    z-index: 2;
}
.heart-gallery .heart-img.show {
    opacity: 1;
    transform: scale(1.08) rotate(-8deg);
    animation: popInHeart 0.7s cubic-bezier(.68,-0.55,.27,1.55);
}
@keyframes popInHeart {
    0% { opacity: 0; transform: scale(0.2) rotate(0deg);}
    60% { opacity: 1; transform: scale(1.2) rotate(10deg);}
    100% { opacity: 1; transform: scale(1.08) rotate(-8deg);}
}
/* Trang lời chúc đẹp - background trong suốt */
.wishes-page {
    position: relative;
    width: 100vw;
    height: 100vh;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    /* Background trong suốt, để hiện background gradient chính của body */
    background: none;
    overflow: hidden;
}

/* Xóa overlay */
.wishes-page::before {
    display: none;
}


/* Trái tim bay đẹp hơn */
.floating-hearts {
    position: absolute;
    top: 0; left: 0;
    width: 100%; height: 100%;
    pointer-events: none;
    z-index: 2;
}

.floating-heart {
    position: absolute;
    font-size: 28px;
    animation: heartFloat 8s linear infinite;
    opacity: 0.9;
    text-shadow: 0 0 15px rgba(255, 255, 255, 0.8);
}

@keyframes heartFloat {
    0% {
        transform: translateY(100vh) rotate(0deg) scale(0.5);
        opacity: 0;
    }
    10% { opacity: 1; }
    50% { transform: translateY(50vh) rotate(180deg) scale(1); }
    90% { opacity: 1; }
    100% {
        transform: translateY(-50px) rotate(360deg) scale(0.5);
        opacity: 0;
    }
}

/* Tiêu đề chính đẹp hơn */
.main-title {
    text-align: center;
    margin-bottom: 30px;
    z-index: 10;
    position: relative;
}

.rainbow-text {
    font-size: 2.0em;
    font-weight: 900;
    background: linear-gradient(45deg, #4649fd, #f141b7, #eeba0f);
    background-size: 800% 800%;
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    animation: rainbowMove 4s ease-in-out infinite;
    text-shadow: 0 0 40px rgba(255, 255, 255, 0.5);
    margin: 0;
    filter: drop-shadow(0 5px 15px rgba(0, 0, 0, 0.3));
}

@keyframes rainbowMove {
    0%, 100% { background-position: 0% 50%; }
    50% { background-position: 100% 50%; }
}

.subtitle {
    /* Cute/feminine handwriting-style font for subtitles */
    font-family: 'Dancing Script', 'Indie Flower', 'Amatic SC', 'Poppins', cursive, 'Segoe UI', Tahoma, sans-serif;
    font-size: 1.7em;
    color: #fff;
    font-weight: 700;
    text-shadow: 0 4px 20px rgba(0, 0, 0, 0.5);
    margin-top: 15px;
    animation: textGlow 3s ease-in-out infinite alternate;
}

@keyframes textGlow {
    from { 
        text-shadow: 0 4px 20px rgba(255, 255, 255, 0.5);
        transform: scale(1);
    }
    to { 
        text-shadow: 0 4px 30px rgba(255, 255, 255, 0.9);
        transform: scale(1.05);
    }
}

/* Bánh sinh nhật cải thiện */
.birthday-cake-section {
    text-align: center;
    margin: 30px 0;
    z-index: 10;
    position: relative;
}

.cake-emoji {
    font-size: 6em;
    animation: cakeBounce 3s ease-in-out infinite;
    filter: drop-shadow(0 15px 25px rgba(0, 0, 0, 0.4));
}

@keyframes cakeBounce {
    0%, 100% { transform: translateY(0) rotate(-3deg) scale(1); }
    50% { transform: translateY(-25px) rotate(3deg) scale(1.1); }
}

.candles {
    display: flex;
    justify-content: center;
    gap: 25px;
    margin-top: -20px;
}

.candle {
    font-size: 2.8em;
    animation: candleFlicker 2s ease-in-out infinite;
    filter: drop-shadow(0 5px 10px rgba(255, 165, 0, 0.6));
}

.candle:nth-child(1) { animation-delay: 0s; }
.candle:nth-child(2) { animation-delay: 0.7s; }
.candle:nth-child(3) { animation-delay: 1.4s; }

@keyframes candleFlicker {
    0%, 100% { transform: scale(1) rotate(-2deg); opacity: 1; }
    50% { transform: scale(1.15) rotate(2deg); opacity: 0.8; }
}

.continue-btn {
    background: linear-gradient(45deg, #ee60ae, #ff9ff3);
    background-size: 600% 600%;
    border: none;
    color: rgb(231, 230, 231);
    padding: 16px 36px;
    font-size: 1.45em;
    /* Use cute handwriting font for the CTA */
    font-family: 'Dancing Script', 'Indie Flower', 'Amatic SC', 'Poppins', cursive, 'Segoe UI', Tahoma, sans-serif;
    font-weight: 600;
    border-radius: 50px;
    cursor: pointer;
    box-shadow: 0 18px 36px rgba(0, 0, 0, 0.22);
    transition: all 0.4s ease;
    animation: buttonGlow 4s ease-in-out infinite;
    z-index: 10;
    position: relative;
    margin-top: 10px; /* Adjusted to move the button higher */
    margin-top: 1px;
    /* softer text styling (no forced uppercase) */
    text-transform: none;
    letter-spacing: 0.6px;
}

@keyframes buttonGlow {
    0%, 100% { 
        background-position: 0% 50%;
        box-shadow: 0 20px 40px rgba(0, 0, 0, 0.3);
        transform: scale(1);
    }
    50% { 
        background-position: 100% 50%;
        box-shadow: 0 25px 60px rgba(255, 107, 107, 0.5);
        transform: scale(1.05);
    }
}

.continue-btn:hover {
    transform: translateY(-8px) scale(1.1);
    box-shadow: 0 30px 60px rgba(0, 0, 0, 0.4);
}

.continue-btn:active {
    transform: translateY(-5px) scale(1.05);
}

/* Responsive cải thiện */
@media (max-width: 768px) {
    .rainbow-text {
        font-size: 2.5em;
    }
    .subtitle {
        font-size: 1.5em;
    }
    .cake-emoji {
        font-size: 5em;
    }
    .continue-btn {
        padding: 18px 45px;
        font-size: 1.5em;
    }
    .card-3d {
        width: 280px;
        height: 380px;
    }
}

/* CSS animation cho confetti rơi */
@keyframes confettiFall {
    0% {
        transform: translateY(-100px) rotate(0deg);
        opacity: 1;
    }
    100% {
        transform: translateY(100vh) rotate(720deg);
        opacity: 0;
    }
}

/* Envelope styles */
.envelope-large {
    width: 520px;
    height: 340px;
    margin: 40px auto 0 auto;
    cursor: pointer;
    z-index: 2;
    perspective: 900px;
    transition: transform 0.2s;
    position: relative;
}

.envelope-large .envelope-body {
    position: absolute;
    bottom: 0;
    left: 0;
    width: 520px;
    height: 220px;
    background: #fff;
    border: 5px solid #fc94bf;
    border-bottom-left-radius: 32px;
    border-bottom-right-radius: 32px;
    z-index: 2;
    box-shadow: 0 16px 48px #e4d0d7aa;
}
.cake-emoji {
    font-size: 6em;
    animation: cakeBounce 3s ease-in-out infinite;
    filter: drop-shadow(0 15px 25px rgba(0, 0, 0, 0.4));
}
.envelope-large .envelope-flap {
    position: absolute;
    top: 0;
    left: 0;
    width: 520px;
    height: 180px;
    background: linear-gradient(135deg, #ffb6d5 80%, #fc94bf 100%);
    clip-path: polygon(0 0, 100% 0, 50% 100%);
    border-top-left-radius: 32px;
    border-top-right-radius: 32px;
    border: 5px solid #fc94bf;
    border-bottom: none;
    z-index: 3;
    box-shadow: 0 8px 24px #ffb6d1aa;
}

.envelope-large .envelope-shadow {
    position: absolute;
    bottom: -24px;
    left: 40px;
    width: 440px;
    height: 44px;
    background: radial-gradient(ellipse at center, #ffb6d155 0%, #fff0 80%);
    border-radius: 50%;
    z-index: 1;
}

.envelope-large .envelope-heart {
    position: absolute;
    left: 50%;
    top: 60%;
    transform: translate(-50%, -50%);
    font-size: 4.5em;
    z-index: 4;
    pointer-events: none;
    filter: drop-shadow(0 2px 12px #ffb6d1aa);
    text-shadow: 0 2px 12px #fff, 0 0 24px #ffb6d1;
}

.envelope-large:hover {
    transform: scale(1.03) rotate(-1deg);
    box-shadow: 0 24px 64px #ffb6d1cc;
}

/* Bubble effects */
.bubbles {
    position: fixed;
    top: 0; left: 0;
    width: 100vw; height: 100vh;
    pointer-events: none;
    z-index: -1;
}

.bubble {
    position: absolute;
    bottom: -50px;
    background: rgba(255, 255, 255, 0.1);
    border-radius: 50%;
    animation: bubbleFloat linear infinite;
}

@keyframes bubbleFloat {
    0% {
        transform: translateY(0) rotate(0deg);
        opacity: 0.8;
    }
    100% {
        transform: translateY(-100vh) rotate(360deg);
        opacity: 0;
    }
}

/* Background hearts */
.bg-hearts {
    position: fixed;
    top: 0; left: 0;
    width: 100vw; height: 100vh;
    pointer-events: none;
    z-index: -1;
}

.bg-heart {
    position: absolute;
    bottom: -50px;
    animation: heartFloatBg linear infinite;
    opacity: 0.7;
}

@keyframes heartFloatBg {
    0% {
        transform: translateY(0) rotate(0deg) scale(1);
        opacity: 0.7;
    }
    50% {
        transform: translateY(-50vh) rotate(180deg) scale(1.2);
        opacity: 1;
    }
    100% {
        transform: translateY(-100vh) rotate(360deg) scale(0.8);
        opacity: 0;
    }
}

/* Hiệu ứng bounce cho chữ "Không còn gì đâu" */
@keyframes textBounce {
    0%, 100% { 
        transform: scale(1) translateY(0); 
    }
    50% { 
        transform: scale(1.05) translateY(-20px); 
    }
}

/* Responsive cho màn hình kết thúc */
@media (max-width: 768px) {
    #endScreen h1 {
        font-size: 3em !important;
        padding: 0 20px;
    }
}

@media (max-width: 480px) {
    #endScreen h1 {
        font-size: 2.2em !important;
        padding: 0 15px;
    }
}

/* Sửa thiệp 3D cho mobile - thay hover bằng active class */
.card-3d.active .card-imgBox,
.card-3d:hover .card-imgBox {
    transform: rotateY(-135deg);
}

.card-3d.active .card-bark,
.card-3d:hover .card-bark {
    opacity: 1;
    transition: 0.8s;
    box-shadow: 300px 200px 100px rgba(255, 105, 180, 0.3) inset;
}

/* Responsive tốt hơn cho mobile */
@media (max-width: 768px) {
    .card-3d {
        width: 280px;
        height: 380px;
        /* Thêm hiệu ứng transform để dễ nhấn hơn */
        transform: perspective(1500px);
    }
    
    .card-3d.active,
    .card-3d:hover {
        transform: perspective(1500px) rotateY(10deg) scale(1.05);
    }
    
    .card-details h4 {
        font-size: 22px;
    }
    
    .card-details p {
        font-size: 13px;
    }
}

@media (max-width: 480px) {
    .card-3d {
        width: 250px;
        height: 340px;
    }
    
    .card-details h4 {
        font-size: 20px;
    }
    
    .card-details p {
        font-size: 12px;
    }
}

/* Hiệu ứng nhấn cho mobile */
@media (max-width: 768px) {
    .card-3d {
        cursor: pointer;
        user-select: none;
        -webkit-tap-highlight-color: transparent;
    }
    
    .card-3d:active {
        transform: perspective(1500px) scale(0.95);
        transition: transform 0.1s ease;
    }
    
    /* Thêm chỉ dẫn cho người dùng */
    .card-3d::after {
        content: '👆 Nhấn để xem lời chúc';
        position: absolute;
        bottom: -40px;
        left: 50%;
        transform: translateX(-50%);
        color: #fff;
        font-size: 14px;
        font-weight: 600;
        text-shadow: 0 2px 8px rgba(0, 0, 0, 0.5);
        animation: tapHint 2s ease-in-out infinite;
        pointer-events: none;
    }
    
    .card-3d.active::after {
        display: none;
    }
}

@keyframes tapHint {
    0%, 100% { 
        opacity: 0.7;
        transform: translateX(-50%) translateY(0);
    }
    50% { 
        opacity: 1;
        transform: translateX(-50%) translateY(-5px);
    }
}

@media (max-width: 768px) {
    .card-3d::after {
        display: none !important;
    }
}
@media (max-width: 768px) {
  body, .card-details, .card-details p, .card-details h4, .main-title, .rainbow-text, .subtitle {
    font-weight: 400;
    letter-spacing: 0.02em;
  }
}
@media (max-width: 480px) {
  body, .card-details, .card-details p, .card-details h4, .main-title, .rainbow-text, .subtitle {
    font-weight: 400;
    letter-spacing: 0.02em;
    -webkit-font-smoothing: antialiased;
  }
}