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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    min-height: 100vh;
    position: relative;
    overflow-x: hidden;
    transition: color 0.8s ease;
}

.sky-background {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: -1;
    transition: background 1s ease;
    transform-origin: center center;
    overflow: hidden;
}

.sky-background.transitioning {
    pointer-events: none;
}

@keyframes skyRotateOut {
    0% {
        transform: rotateY(0deg);
        opacity: 1;
    }
    100% {
        transform: rotateY(90deg);
        opacity: 0;
    }
}

@keyframes skyRotateIn {
    0% {
        transform: rotateY(-90deg);
        opacity: 0;
    }
    100% {
        transform: rotateY(0deg);
        opacity: 1;
    }
}

.sky-background.rotating-out {
    animation: skyRotateOut 0.6s ease-in-out;
}

.sky-background.rotating-in {
    animation: skyRotateIn 0.6s ease-in-out;
}

@keyframes darknessWave {
    0% {
        clip-path: polygon(0 0, 0 0, 0 100%, 0 100%);
    }
    100% {
        clip-path: polygon(0 0, 100% 0, 100% 100%, 0 100%);
    }
}

.sky-background.darkness-wave::before {
    content: '';
    position: absolute;
    top: -10%;
    left: -10%;
    width: 120%;
    height: 120%;
    background: linear-gradient(135deg,
        rgba(12, 20, 69, 0) 0%,
        rgba(12, 20, 69, 0.3) 20%,
        rgba(12, 20, 69, 0.7) 50%,
        #0c1445 80%
    );
    animation: darknessWave 1.5s cubic-bezier(0.4, 0.0, 0.2, 1) forwards;
    z-index: 1;
}

@keyframes lightSweep {
    0% {
        clip-path: polygon(100% 100%, 100% 100%, 100% 100%, 100% 100%);
    }
    100% {
        clip-path: polygon(0 0, 100% 0, 100% 100%, 0 100%);
    }
}

.sky-background.light-sweep::before {
    content: '';
    position: absolute;
    top: -10%;
    left: -10%;
    width: 120%;
    height: 120%;
    background: linear-gradient(-45deg,
        rgba(135, 206, 235, 0) 0%,
        rgba(135, 206, 235, 0.3) 20%,
        rgba(135, 206, 235, 0.7) 50%,
        #87CEEB 80%
    );
    animation: lightSweep 1.5s cubic-bezier(0.4, 0.0, 0.2, 1) forwards;
    z-index: 1;
}

.sky-background.darkness-wave .moon {
    filter: drop-shadow(0 0 30px rgba(255, 255, 255, 0.8));
}

.sky-background.light-sweep .sun {
    filter: drop-shadow(0 0 40px rgba(255, 215, 0, 0.9));
}

body[data-theme="light"] .sky-background {
    background: linear-gradient(to bottom,
        #87CEEB 0%,
        #98D8E8 50%,
        #B0E2FF 100%
    );
}

body[data-theme="dark"] .sky-background {
    background: linear-gradient(to bottom,
        #0c1445 0%,
        #1a1f4a 50%,
        #2d3561 100%
    );
}

body[data-theme="dusk"] .sky-background {
    background: linear-gradient(to bottom,
        #ff6b6b 0%,
        #ff8c42 30%,
        #ffa94d 60%,
        #ffd97d 100%
    );
}

body[data-theme="dawn"] .sky-background {
    background: linear-gradient(to bottom,
        #f9a8d4 0%,
        #fbbfd4 30%,
        #ffd6a5 60%,
        #ffe8b8 100%
    );
}

.celestial-body {
    position: absolute;
    width: 80px;
    height: 80px;
    border-radius: 50%;
    transition: all 1.5s cubic-bezier(0.4, 0.0, 0.2, 1);
    opacity: 0;
    z-index: 2;
    will-change: transform, opacity, left, top;
}

.sun {
    background: radial-gradient(circle, #FFD700 0%, #FFA500 100%);
    box-shadow: 0 0 60px rgba(255, 215, 0, 0.8),
                0 0 100px rgba(255, 215, 0, 0.4),
                inset 0 0 20px rgba(255, 255, 255, 0.5);
}

.moon {
    background: radial-gradient(circle, #F0F0F0 0%, #C0C0C0 100%);
    box-shadow: 0 0 40px rgba(255, 255, 255, 0.6),
                0 0 80px rgba(255, 255, 255, 0.3),
                inset -10px -10px 20px rgba(150, 150, 150, 0.3);
}

body[data-theme="light"] .sun {
    opacity: 1;
    top: 15%;
    left: 80%;
    transform: rotate(0deg);
}

body[data-theme="light"] .moon {
    opacity: 0;
}

body[data-theme="dark"] .moon {
    opacity: 1;
    top: 10%;
    left: 85%;
}

body[data-theme="dark"] .sun {
    opacity: 0;
}

body[data-theme="dusk"] .sun {
    opacity: 1;
    top: 60%;
    left: 10%;
}

body[data-theme="dusk"] .moon {
    opacity: 0.3;
    top: 20%;
    left: 85%;
}

body[data-theme="dawn"] .sun {
    opacity: 1;
    top: 60%;
    left: 85%;
}

body[data-theme="dawn"] .moon {
    opacity: 0.2;
    top: 15%;
    left: 15%;
}

.clouds {
    position: absolute;
    width: 100%;
    height: 100%;
    opacity: 0;
    transition: opacity 1.5s ease;
    overflow: hidden;
    z-index: 1;
    pointer-events: none;
}

body[data-theme="light"] .clouds,
body[data-theme="dawn"] .clouds {
    opacity: 1;
}

.cloud {
    position: absolute;
    background: rgba(255, 255, 255, 0.7);
    border-radius: 100px;
    box-shadow: 0 8px 20px rgba(0, 0, 0, 0.1);
}

.cloud::before,
.cloud::after {
    content: '';
    position: absolute;
    background: rgba(255, 255, 255, 0.7);
    border-radius: 100px;
}

.cloud::before {
    width: 50px;
    height: 50px;
    top: -25px;
    left: 10px;
}

.cloud::after {
    width: 60px;
    height: 60px;
    top: -30px;
    right: 10px;
}

.cloud-1 {
    width: 100px;
    height: 40px;
    top: 15%;
    left: -150px;
    animation: drift 45s linear infinite;
}

.cloud-2 {
    width: 80px;
    height: 35px;
    top: 25%;
    left: -120px;
    animation: drift 35s linear infinite 5s;
}

.cloud-3 {
    width: 60px;
    height: 28px;
    top: 40%;
    left: -100px;
    animation: drift 28s linear infinite 10s;
}

.cloud-4 {
    width: 90px;
    height: 38px;
    top: 55%;
    left: -130px;
    animation: drift 40s linear infinite 15s;
}

.cloud-5 {
    width: 110px;
    height: 42px;
    top: 70%;
    left: -140px;
    animation: drift 38s linear infinite 8s;
}

@keyframes drift {
    0% {
        transform: translateX(0);
    }
    100% {
        transform: translateX(calc(100vw + 200px));
    }
}

.sky-background.darkness-wave .clouds {
    opacity: 0;
    transition: opacity 0.8s ease-out;
}

.sky-background.light-sweep .clouds {
    opacity: 1;
    transition: opacity 1.2s ease-in 0.5s;
}

.stars {
    position: absolute;
    width: 100%;
    height: 100%;
    opacity: 0;
    transition: opacity 1.5s ease;
    overflow: hidden;
    z-index: 0;
}

body[data-theme="dark"] .stars {
    opacity: 1;
}

@keyframes twinkle {
    0%, 100% {
        opacity: 0.3;
    }
    50% {
        opacity: 1;
    }
}

.stars::before {
    animation: twinkle 3s ease-in-out infinite;
}

.stars::after {
    animation: twinkle 4s ease-in-out infinite 1s;
}

.stars::before,
.stars::after {
    content: '';
    position: absolute;
    width: 100%;
    height: 100%;
    background-image:
        radial-gradient(2px 2px at 10% 15%, white, transparent),
        radial-gradient(2px 2px at 25% 25%, white, transparent),
        radial-gradient(1px 1px at 40% 10%, white, transparent),
        radial-gradient(2px 2px at 55% 30%, white, transparent),
        radial-gradient(1px 1px at 70% 20%, white, transparent),
        radial-gradient(2px 2px at 85% 35%, white, transparent),
        radial-gradient(1px 1px at 92% 12%, white, transparent),
        radial-gradient(2px 2px at 15% 45%, white, transparent),
        radial-gradient(1px 1px at 30% 55%, white, transparent),
        radial-gradient(2px 2px at 45% 50%, white, transparent),
        radial-gradient(1px 1px at 60% 60%, white, transparent),
        radial-gradient(2px 2px at 75% 48%, white, transparent),
        radial-gradient(1px 1px at 88% 58%, white, transparent),
        radial-gradient(2px 2px at 95% 42%, white, transparent),
        radial-gradient(1px 1px at 18% 75%, white, transparent),
        radial-gradient(2px 2px at 35% 80%, white, transparent),
        radial-gradient(1px 1px at 52% 72%, white, transparent),
        radial-gradient(2px 2px at 68% 85%, white, transparent),
        radial-gradient(1px 1px at 82% 78%, white, transparent),
        radial-gradient(2px 2px at 93% 88%, white, transparent),
        radial-gradient(1px 1px at 8% 92%, white, transparent),
        radial-gradient(2px 2px at 22% 95%, white, transparent),
        radial-gradient(1px 1px at 48% 90%, white, transparent),
        radial-gradient(2px 2px at 65% 96%, white, transparent),
        radial-gradient(1px 1px at 78% 93%, white, transparent),
        radial-gradient(2px 2px at 90% 97%, white, transparent);
    background-size: 100% 100%;
    background-repeat: no-repeat;
}

.stars::after {
    background-image:
        radial-gradient(1px 1px at 5% 8%, white, transparent),
        radial-gradient(2px 2px at 20% 18%, white, transparent),
        radial-gradient(1px 1px at 38% 22%, white, transparent),
        radial-gradient(2px 2px at 50% 15%, white, transparent),
        radial-gradient(1px 1px at 65% 28%, white, transparent),
        radial-gradient(2px 2px at 78% 12%, white, transparent),
        radial-gradient(1px 1px at 95% 25%, white, transparent),
        radial-gradient(2px 2px at 12% 38%, white, transparent),
        radial-gradient(1px 1px at 28% 48%, white, transparent),
        radial-gradient(2px 2px at 42% 42%, white, transparent),
        radial-gradient(1px 1px at 58% 52%, white, transparent),
        radial-gradient(2px 2px at 72% 45%, white, transparent),
        radial-gradient(1px 1px at 85% 55%, white, transparent),
        radial-gradient(2px 2px at 97% 48%, white, transparent),
        radial-gradient(1px 1px at 15% 68%, white, transparent),
        radial-gradient(2px 2px at 32% 72%, white, transparent),
        radial-gradient(1px 1px at 48% 78%, white, transparent),
        radial-gradient(2px 2px at 62% 70%, white, transparent),
        radial-gradient(1px 1px at 80% 82%, white, transparent),
        radial-gradient(2px 2px at 88% 75%, white, transparent),
        radial-gradient(1px 1px at 25% 88%, white, transparent),
        radial-gradient(2px 2px at 40% 92%, white, transparent),
        radial-gradient(1px 1px at 55% 85%, white, transparent),
        radial-gradient(2px 2px at 70% 95%, white, transparent),
        radial-gradient(1px 1px at 85% 90%, white, transparent),
        radial-gradient(2px 2px at 98% 92%, white, transparent);
    background-size: 100% 100%;
    background-repeat: no-repeat;
}

.theme-toggle {
    position: fixed;
    top: 20px;
    right: 20px;
    display: flex;
    gap: 10px;
    background: rgba(255, 255, 255, 0.15);
    backdrop-filter: blur(10px);
    padding: 10px;
    border-radius: 50px;
    z-index: 100;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.1);
}

.theme-btn {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 4px;
    padding: 12px 16px;
    border: none;
    border-radius: 30px;
    background: transparent;
    cursor: pointer;
    transition: all 0.3s ease;
    color: rgba(255, 255, 255, 0.8);
    font-size: 0.75rem;
    font-weight: 600;
}

body[data-theme="light"] .theme-btn {
    color: rgba(0, 0, 0, 0.7);
}

.theme-btn .icon {
    font-size: 1.5rem;
}

.theme-btn:hover {
    background: rgba(255, 255, 255, 0.2);
    transform: translateY(-2px);
}

body[data-theme="light"] .theme-btn:hover {
    background: rgba(0, 0, 0, 0.1);
}

.theme-btn.active {
    background: rgba(255, 255, 255, 0.3);
    color: white;
}

body[data-theme="light"] .theme-btn.active {
    background: rgba(0, 0, 0, 0.15);
    color: black;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 60px 20px;
    position: relative;
    z-index: 1;
}

.hero {
    text-align: center;
    margin-bottom: 80px;
    padding: 60px 20px;
}

.title {
    font-size: 4rem;
    font-weight: 700;
    margin-bottom: 20px;
    text-shadow: 2px 2px 8px rgba(0, 0, 0, 0.2);
    color: rgba(255, 255, 255, 0.95);
    transition: color 0.8s ease;
}

body[data-theme="light"] .title {
    color: rgba(0, 0, 0, 0.85);
    text-shadow: 2px 2px 4px rgba(255, 255, 255, 0.5);
}

.subtitle {
    font-size: 1.5rem;
    margin-bottom: 40px;
    color: rgba(255, 255, 255, 0.85);
    transition: color 0.8s ease;
}

body[data-theme="light"] .subtitle {
    color: rgba(0, 0, 0, 0.7);
}

.start-btn {
    display: inline-block;
    padding: 18px 50px;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    text-decoration: none;
    border-radius: 50px;
    font-size: 1.3rem;
    font-weight: 600;
    transition: all 0.3s ease;
    box-shadow: 0 10px 30px rgba(102, 126, 234, 0.4);
}

.start-btn:hover {
    transform: translateY(-3px);
    box-shadow: 0 15px 40px rgba(102, 126, 234, 0.6);
}

.features {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 30px;
    margin-bottom: 60px;
}

.feature-card {
    background: rgba(255, 255, 255, 0.15);
    backdrop-filter: blur(10px);
    padding: 40px 30px;
    border-radius: 20px;
    text-align: center;
    transition: all 0.3s ease;
    border: 1px solid rgba(255, 255, 255, 0.2);
    color: rgba(255, 255, 255, 0.95);
}

body[data-theme="light"] .feature-card {
    background: rgba(255, 255, 255, 0.5);
    border: 1px solid rgba(0, 0, 0, 0.1);
    color: rgba(0, 0, 0, 0.85);
}

.feature-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 15px 40px rgba(0, 0, 0, 0.2);
}

body[data-theme="light"] .feature-card:hover {
    box-shadow: 0 15px 40px rgba(0, 0, 0, 0.15);
}

.feature-icon {
    font-size: 3rem;
    margin-bottom: 20px;
}

.feature-card h3 {
    font-size: 1.5rem;
    margin-bottom: 15px;
    color: inherit;
}

.feature-card p {
    color: inherit;
    opacity: 0.9;
    line-height: 1.6;
}

.footer {
    text-align: center;
    padding: 40px 20px;
    color: rgba(255, 255, 255, 0.7);
    transition: color 0.8s ease;
}

body[data-theme="light"] .footer {
    color: rgba(0, 0, 0, 0.6);
}

@media (max-width: 768px) {
    .title {
        font-size: 2.5rem;
    }

    .subtitle {
        font-size: 1.2rem;
    }

    .start-btn {
        padding: 15px 40px;
        font-size: 1.1rem;
    }

    .theme-toggle {
        top: 10px;
        right: 10px;
        padding: 8px;
        gap: 6px;
    }

    .theme-btn {
        padding: 10px 12px;
    }

    .theme-btn .label {
        font-size: 0.7rem;
    }

    .features {
        grid-template-columns: 1fr;
    }
}