:root {
    --bg-color: #f0f4f8;
    --text-color: #1a1a1a;
    --card-color: #fff;
    --accent-color: #00bfa6;
    --input-bg: #e0e7ef;
}

body.dark {
    --bg-color: #1a1a2e;
    --text-color: #fff;
    --card-color: #252841;
    --accent-color: #2882c7;
    --input-bg: #33354d;
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

body {
    background: var(--bg-color);
    color: var(--text-color);
    margin: 0;
    min-height: 100vh;
    padding: 2em;
    transition: all 0.4s ease;
}

.container {
    max-width: 500px;
    margin: auto;
    text-align: center;
}

.container h1 {
    margin-bottom: 20px;
}

.card {
    background: var(--card-color);
    padding: 2em;
    border-radius: 16px;
    box-shadow: 0 10px 25px rgba(0,0,0,0.1);
    animation: slideIn 0.4s ease-in-out;
}

@keyframes slideIn {
    from {
        transform: translateY(100px);
        opacity: 0;
    } to {
        transform: translateY(0);
        opacity: 1;
    }
}

input, button {
    padding: 0.75em;
    border: none;
    margin: 0.5em 0;
    font-size: 1em;
    font-weight: bold;
    color: var(--text-color);
    border-radius: 10px;
    width: 100%;
    background: var(--input-bg);
    transition: all 0.2s ease;
}

input:focus, button:hover {
    outline: none;
    transform: scale(1.03);
}

label {
    font-weight: bold;
}

.tip-options {
    display: flex;
    gap: 0.5em;
    flex-wrap: wrap;
    justify-content: center;
    margin-top: 0.5em;
}

.tip-btn {
    background: var(--accent-color);
    color: #fff;
    flex: 1;
    cursor: pointer;
}

#toggle-theme {
    background: none;
    border: 2px solid var(--text-color);
    color: var(--text-color);
    cursor: pointer;
    margin-bottom: 1em;
}

.results {
    margin-top: 1.5em;
    font-size: 1.2em;
    animation: fadeIn 0.6s ease-in;
}

@keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
}

.actions {
    margin-top: 1em;
}